ශ්‍රි ලාංකේය පාඨක ඔබ සෑමට ඉතා අභිමානයෙන් ඉදිරිපත් කෙරෙන මෙම වෙබ් අඩවියෙහි, අප දැන ගත යුතු ප්‍රධාන ඛණිජ ද්‍රව්‍යයක් වන මැණික් පිලිබදව පැහැදිලි සහ නිරවද්‍ය තොරතුරු ඉදිරිපත් කරමි.
මෙහි එන සියලු කරුණු පාඨක ඔබ කුතුහලයට පත් නොකොට අවබෝධ කර ගත හැකි පරිදි සරලව ලබා දීමට කටයුතු කරමි.මෙහි දී සෑම කරුණක්ම අන්තර ජාලය පරික්ෂා කිරිමෙන් සහ අනිකුත් වැදගත් ලෙඛණ ඇසුරෙන් ඔබ වෙත ඉදිරිපත් කිරීම තුළින් ශ්‍රි ලාංකා මැණික් පිළිබදව සරල හෝ දැනුමක් ලැබෙතැයි මා විශ්වාස කරමි.
අන්තර්ජාලයේ ඇති සියලුම කරුණු ඉංග්‍රිසී භාෂාවෙන් ඈති අතර ,ඒවා පැහැදිලි සිංහල භාෂාවට පර්වර්තනය කිරීමේදි සුලු ප්‍රමාද දෝෂ තිබිය හැකිය. සමහර ඉංග්‍රිසී වචන වල තේරුම පාරිභාෂික සිංහල භාෂාවේ නොමති විට එහි පොදු වචනය පමණක් යොදා ගමි.
ඓතිහාසික සිදුවීම් විස්තර කිරීමේදි මිත්‍යා මත පවතින අතර ඒවා යථාර්ථවාදීව පවතින අදහස් පමණක් මෙම ලපි වලට යොදා ගතිමි.
ලොව හැඩ කරනා මිල කළ නොහැකි අපේ මැණික්
(කොළඹ, ලංකාපුවත්) ශ්‍රී ලංකාවේ අද වන විට මැණික් හා ස්වර්ණාභරණ කර්මාන්තය ප්‍රධාන තැනක් ගනියි. මෙරට පමණක් නොව, මැණික් අද ලෝකයේ ප්‍රධාන කරුණු තුනක් හේතුවෙන් ඉතා වැදගත් වටිනාකමකින් යුතු ඛනිජ ද්‍රව්‍යක් බවට පත් වී ඇත. මෙම කරුණු තුනෙන් එකක් වනුයේ, එහි ඇති අලංකාරය යි. පාෂාණයක අලංකාරය පිළිබඳ අගය කිරීමෙන් සිදු කරනුයේ එහි පාරදෘෂ්‍ය බවත්, වර්ගයත්, පිළිබඳ සළකා බැලීමෙනි. මැණික් කපා ඔප දැමීමෙක් එහි අලංකාරය වැඩි වේ. දෙවැනි කාරුණය නම්, එහි කල්පවතින ස්වභාවය යි. ආභරණ සඳහා පළඳින කපා ඔප දැමු මැණික් එම ස්වභායෙන්ම කාලයක් පැවතීම එහි ආර්ථික වටිනාකම වැඩි කරන සාධකයකි. ඛනිජ වර්ග බොහෝ විට සුලභ වුවද මැණික් ඉතා දුර්ලභ ගණයේ ඛනිජ ද්‍රව්‍යයකි. මෙම හේතුව නිසාද මැණික් නම් ඛනිජ වර්ගයේ වටිනාකම වැඩිවීමට බලපා තිබේ. මේ අනුව අද ලෝකයේ මැණික් සඳහා ඉහළ අර්ථික වටිනාකමක් ලැබී ඇත.
ශ්‍රී ලංකාවේ විශේෂයෙන් සබරගමු පළාතේ මැණික් කර්මාන්තයට හිමි වන්නේ අද්විතීය ස්ථානයකි. අනාදිමත් කාලයක සිට ලංකාව ලෝකය පුරා ප්‍රචලිතවීමට හේතුවක් වූයේද මෙම අගනා ඛනිජ ද්‍රව්‍යය යි. ‘රත්නදීපය’, ‘රත්නදේශය’ ආදි නම්වලින් මෙරට හැඳින්වූයේද මෙම මැණික් ව්‍යාපාරයක් ලෙස අතීතයේ සිට ප්‍රචලිතව පැවතීම නිසාය. 1292දී මාර්කෝ පෝලෝ විසින් සිය ලිපියක ලංකාව ගැන සඳහන් කර තිබූයේ, “ප්‍රමාණයෙන් තරමක් කුඩා වුවත් ඉතා අනර්ඝ දිවයිනක් වූ ශ්‍රී ලංකාවේ ඇල දොළ ගංගා වලින් පවා මුතු මැණික් හමු වේ” ලෙසයි. දෙවන ශත වර්ශයේ විසූ ටොලමි විසින් සඳහන් කරන පරිදි අතීතයේ ලංකාවේ මැණික් 
කර්මාන්තයේ මූලික ස්ථානයක් හිමිව තිබුනේ ‘තරිප්පු’ (beryl) සහ ‘කොරන්ඩම්’ (sapphire) වලටය. සිව්වන සහ පස්වන ශතවර්ශ වලදී පර්සියානු සහ අරාබි වෙළඳුන් මුතු මැණික් වෙළඳාම සඳහා ලංකාවට පැමිණි බවද සඳහන් වේ.
පසුගිය නොවැම්බර් මාසයේදි බ්‍රිතාන්‍යයේ වාර්තා වූ පුවතක් හේතුවෙන් මෙරට මැණික් සඳහා ජාත්‍යන්තරයේ මෙරට මැණික් සඳහා වූ ඉල්ලුම තව තවත් වැඩි කිරීමට සමත් විය. එනම් එංගලන්තයේ ඔටුන්නහිමි කුමරු වන විලියම් කුමරු සිය සහකාරිය වන කැතරින් මිඩ්ල්ටන් හෙවත් කේට් හට පළඳවන ලද මුදුවේ ඔබ්බවා ඇති නිල් මැණික ශ්‍රී ලංකාවේ මැණිකක් බව අනාවරණය වීමෙනි. විවාහ ගිවිස ගැනීමේ මුදුවලින් ලොව මෙතෙක් වැඩිපුරම කතාබහට ලක් වූ මුදුව මෙය යි. මෙම මුද්ද විලියම් කුමරුගේ පියා වන චාල්ස් කුමරු විසින් ඩයනා කුමරියට පළඳන ලද මුදුවම වන අතර මෙම මුදුවෙහි ඔබ්බවා තිබෙන නිල් මැණික් ගල ශ්‍රී ලංකාවෙන් ලබාගෙන ඇති ඉහල වටිනාකමකින් යුත් බ්ලූ සෆායර් වර්ගයේ මැණිකක් වන බව බ්‍රිතාන්‍යයේ මාධ්‍ය වාර්තා රැසක සඳහන් විය.
ලන්ඩනයේ ඩේලි මේල් සහ නැෂනල් ජියොග්‍රැෆි නාලිකාව සඳහන් කරන පරිදි මෙම ගල කැරට් 12කින් යුක්ත වන අතර එය වටා තවත් දියමන්ති 14ක් ඔබ්බවා කැරට් දහ අටේ සුදු රත්රං වලින් මෙම මුදුව නිමවා තිබේ. දශක 3කට පෙර මෙහි මිල පවුම් 28500ක් වූ බවත් 1997 ඩයනා කුමරියගේ අභාවය සිදුවන අවස්ථාවේදී එහි වටිනාකම 8 ගුණයකින් ඉහල ගොස් ඇති බවත් වාර්තා වේ. මෙම මුදුව පිළිබඳ තොරතුරු අනාවරණය වීමත් සමග මෙරට මැණික් පිළිබඳව ජාත්‍යන්තර වශයෙන් විශාල අවධානයක් යොමුවී ඇත. තවද එංගලන්තයේ දෙවැනි එලිසබෙත් රැජින පළඳින ඔටුන්නේ තිබෙන ශාන්ත එඩ්වඩ් නිල් මැණික ද ශ්‍රී ලංකාවේ මැණිකක් බව මෙරට මාධ්‍යවලින් වාර්තා විය. මැණික් විශේෂඥයින්
පවසන්නේ විවාහ ගිවිස ගැනීමේ මුදුවේ හා අධිරාජ්‍ය ඔටුන්න යන දෙකෙහිම තිබෙන නිල් මැණික් ශ්‍රී ලංකාවේ රත්නපුර ප්‍රදේශයේ දියලු ඔප කුඩු නිධිවලින් පැවතගෙන එන ඒවා බවයි. ලෝකවේ වටිනාකමින් අධික මැණික් අතරට එක්වූ 1907දී කුරුවිට ප්‍රදේශයෙන් හමු වූ කැරට් 466කින් යුතු නිල් මැණිකක් ඇමරිකාවේ කෞතුකාගාරයක මහජන ප්‍ර්‍රදර්ශනයට තබා ඇත.
ශ්‍රී ලංකාවේ මැණික් ප්‍රභේද වැඩි ප්‍රමාණක් පිහිටා ඇත්තේ රත්නපුර ප්‍රදේශයේය. එසේම සබරගමු නාමයද ව්‍යවහාරයට පැමිණියේ පුරාණයේ මෙහි පැමිණි ග්‍රීක සංචාරකයන්ගේ සිත්ගත් මැණික් යන අර්ථය දෙන ‘සැෆිරස්’ යන ග්‍රීක වචනය මුල්කරගෙන බව පැවසේ. සබරගමු පළාතේ රත්නපුර, පැල්මඩුල්ල, කුරුවිට, බලංගොඩ ආදි ප්‍රදේශවල මැණික් බහුල වන අතර මේ හැර සිංහරාජ, මොරපිටිය, දෙණියාය, අකුරැස්ස, බුලත්සිංහල, හිනිදුම, ඇළහැර, ඔක්කම්පිටිය ප්‍රදේශ වලින්ද මැණික් හමුවෙයි.
ශ්‍රී ලංකාවේ මැණික් ගල් ප්‍රාග් කේම්බ්‍රීය යුගයේ හටගෙන ඇති බවට සැළකෙන අතර මෙරට මැණික් ප්‍රභේද හතලිහකට වැඩි ප්‍රමාණයක් ඇත. කොරන්ඩම් ඒ අතර හමුවන දීප්තිමත් වර්ණයන්ගෙන් යුත් මැණික් විශේෂයකි. පුෂ්පරාග මේ වර්ගයේ මැණිකක් වන අතර එය කහ වර්ණයෙන් යුක්ත වෙයි. ළා රෝස පැහැති පද්මරාග, නිල් හා රතු ආරුනූල් ද මේ වර්ගයේ මැණික් වෙයි. කනක නම් තවත් මැණික් වර්ගයක් මෙරටින් හමුවන අතර වෛරෝඩි, 
පසිංගල් මේ වර්ගයට අයත් වේ. මේවා ළා කොළ, තද කොළ පැහැයන්ගෙන් යුතු වෙයි. එසේම පදියං නැමැති මැණික් වර්ගයක් ලංකාවේ දක්නට ලැබෙන 
අතර කොළ, කහ, දුඹුරු හා ළා රතු පැහැති ජාගුන් නම් මැණික් වර්ගයද මෙරටින් හමු වෙයි. රබහ තවත් මැණික් විශේෂයක් වන අතර ඒවා ළා රත් පැහැයෙන් යුක්ත වේ. ගෝමේද මේ වර්ගයට අයත්වෙයි. පළිඟු නම් මැණික් වර්ගයක්ද වන අතර මේවා කහ, සුදු හා රෝස වර්ණයන්ගෙන් යුක්ත වේ. එසේම තෝරමල්ලි, පුන්ක්කන්,
දියතරිප්පු, ලෙස තවත් මැණික් වර්ග ශ්‍රී ලංකාවේ දක්නට ලැබේ. නිල් මැණික්, රතු මැණික් හා වෛරෝඩි ශ්‍රී ලංකාවේ ඉහළ ඉල්ලූමක් ඇති මැණික් ගල් අතරට අයත් වේ.
ස්වභාවිකව හමුවන මැණික් ඝර්ෂණයට හා ඛාදනයට ලක්වීමෙන් ඒවායේ ස්ඵටික ස්වභාවයෙන් ඈත් වී විෂමහාකාර හැඩවලින් යුක්ත වේ. එසේ නමුදු ඒවා කපා ඔප දැමීමෙන් එහි දිස්නය මෙන්ම වර්ණවත් බව ද වැඩි කළ හැකිය. මෙසේ සකස් කිරීමෙන් අනතුරුව ඒවාට ඉහළ වෙළෙඳ වටිනාකමක් හිමි වෙයි. මැණිකක් තක්සේරු කිරීමේදි භාවිත කරන ප්‍රධාන මිනුම් නම්, එහි පැහැයේ ගැඹුර, පිරිසිදු බව, පාරදෘෂ්‍ය බව, ප්‍රභාව හා පළුදුවලින් තොර බවයි. රත්රං මෙන්ම මැණික්වල බර මැනීමේදි ඉතා සංවේදි තරාදි භාවිත කරනු ලැබේ. මිනුම් ඒකක ලෙස ක්‍රාත් හෙවත් කැරට් යොදා ගනු ලබයි. ක්‍රාත් එකක් මිලිග්‍රෑම් 200කට සමාන වේ. මෙය අන්තර්ජාතික කිරුම් ඒකකය ලෙස භාවිතයට ගැනේ.
ශ්‍රී ලංකාවට විදේශ විනිමය ගෙනෙන දේ අතර මැණික් හා ස්වර්ණාභරණ කර්මාන්තය ප්‍රධාන තැනක් ගනී. මෙහිදි මැණික් ඉල්ලම් ප්‍රමාණය දිනෙන් දින අඩු වීම, ඉල්ලම් හෑරිමේ අපහසුතා, පහසුකම් අඩුවීම ආදිය නිසා අද වන විට ඉල්ලුමට සරිලන සැපයුමක් ලබාදීමට අපොහොසත්වන තත්ත්වයකට පත්වී ඇත. මීට අමතරව නිසි ක්‍රමවේදයකින් බැහැරව අවිධිමත් ලෙස සිදුකරන මැණික් පතල් හේතුවෙන් පරිසරය මෙන්ම මිනිස් ජීවිත විනාශ වූ අවස්ථාද බොහෝ දක්නට ලැබේ. තවද දැඩි අවදානම් මෙම මැණික් පතල් කර්මාන්නතයේ නියැලෙන්නන්ගේ ජීවිත සුරක්ෂිත කිරීමටද විශේෂ වැඩපිළිවෙලක් ක්‍රියාත්මක කළ යුතුව ඇත. එසේම මැණික් ඉල්ලම් සහිත ප්‍රදේශ
හඳුනාගැනීමේ ක්‍රමවේදයක් ඇති කළ යුතු කාලයද එළඹ ඇත. මේ අනුව මැණික් ඉල්ලම් බහුල ප්‍රදේශ පමණක් තෝරා ගනිමින් මෙම කර්මාන්තය සිදු කිරීමෙන් වෙනත් ප්‍රයෝජනයක් සඳහා ගත හැකිවීමට ඇති භූමිය විනාශ වීම මෙන්ම මුදල් නාස්තිය අවම කරගත හැකි වනු ඇත. කෙතරම් අලංකාර වුවද කෙතරම් වටිනා වුවද මෙරටට කෙතෙරම් විදේශ විනිමයක් රැස් කර දුන්නත් මේ හේතුවෙන් සිදුවන්නේ භූගත භූමිය කුහරයක් බවට පත්වීම පමණි.
කර්මාන්තයේ මූලික ස්ථානයක් හිමිව තිබුනේ ‘තරිප්පු’ (beryl) සහ ‘කොරන්ඩම්’ (sapphire) වලටය. සිව්වන සහ පස්වන ශතවර්ශ වලදී පර්සියානු සහ අරාබි වෙළඳුන් මුතු මැණික් වෙළඳාම සඳහා ලංකාවට පැමිණි බවද සඳහන් වේ.පසුගිය නොවැම්බර් මාසයේදි බ්‍රිතාන්‍යයේ වාර්තා වූ පුවතක් හේතුවෙන් මෙරට මැණික් සඳහා ජාත්‍යන්තරයේ මෙරට මැණික් සඳහා වූ ඉල්ලුම තව තවත් වැඩි කිරීමට සමත් විය. එනම් එංගලන්තයේ ඔටුන්නහිමි කුමරු වන විලියම් කුමරු සිය සහකාරිය වන කැතරින් මිඩ්ල්ටන් හෙවත් කේට් හට පළඳවන ලද මුදුවේ ඔබ්බවා ඇති නිල් මැණික ශ්‍රී ලංකාවේ මැණිකක් බව අනාවරණය වීමෙනි. විවාහ ගිවිස ගැනීමේ මුදුවලින් ලොව මෙතෙක් වැඩිපුරම කතාබහට ලක් වූ මුදුව මෙය යි. මෙම මුද්ද විලියම් කුමරුගේ පියා වන චාල්ස් කුමරු විසින් ඩයනා කුමරියට පළඳන ලද මුදුවම වන අතර මෙම මුදුවෙහි ඔබ්බවා තිබෙන නිල් මැණික් ගල ශ්‍රී ලංකාවෙන් ලබාගෙන ඇති ඉහල වටිනාකමකින් යුත් බ්ලූ සෆායර් වර්ගයේ මැණිකක් වන බව බ්‍රිතාන්‍යයේ මාධ්‍ය වාර්තා රැසක සඳහන් විය.
ලන්ඩනයේ ඩේලි මේල් සහ නැෂනල් ජියොග්‍රැෆි නාලිකාව සඳහන් කරන පරිදි මෙම ගල කැරට් 12කින් යුක්ත වන අතර එය වටා තවත් දියමන්ති 14ක් ඔබ්බවා කැරට් දහ අටේ සුදු රත්රං වලින් මෙම මුදුව නිමවා තිබේ. දශක 3කට පෙර මෙහි මිල පවුම් 28500ක් වූ බවත් 1997 ඩයනා කුමරියගේ අභාවය සිදුවන අවස්ථාවේදී එහි වටිනාකම 8 ගුණයකින් ඉහල ගොස් ඇති බවත් වාර්තා වේ. මෙම මුදුව පිළිබඳ තොරතුරු අනාවරණය වීමත් සමග මෙරට මැණික් පිළිබඳව ජාත්‍යන්තර වශයෙන් විශාල අවධානයක් යොමුවී ඇත. තවද එංගලන්තයේ දෙවැනි එලිසබෙත් රැජින පළඳින ඔටුන්නේ තිබෙන ශාන්ත එඩ්වඩ් නිල් මැණික ද ශ්‍රී ලංකාවේ මැණිකක් බව මෙරට මාධ්‍යවලින් වාර්තා විය. මැණික් විශේෂඥයින්
පවසන්නේ විවාහ ගිවිස ගැනීමේ මුදුවේ හා අධිරාජ්‍ය ඔටුන්න යන දෙකෙහිම තිබෙන නිල් මැණික් ශ්‍රී ලංකාවේ රත්නපුර ප්‍රදේශයේ දියලු ඔප කුඩු නිධිවලින් පැවතගෙන එන ඒවා බවයි. ලෝකවේ වටිනාකමින් අධික මැණික් අතරට එක්වූ 1907දී කුරුවිට ප්‍රදේශයෙන් හමු වූ කැරට් 466කින් යුතු නිල් මැණිකක් ඇමරිකාවේ කෞතුකාගාරයක මහජන ප්‍ර්‍රදර්ශනයට තබා ඇත.
ශ්‍රී ලංකාවේ මැණික් ප්‍රභේද වැඩි ප්‍රමාණක් පිහිටා ඇත්තේ රත්නපුර ප්‍රදේශයේය. එසේම සබරගමු නාමයද ව්‍යවහාරයට පැමිණියේ පුරාණයේ මෙහි පැමිණි ග්‍රීක සංචාරකයන්ගේ සිත්ගත් මැණික් යන අර්ථය දෙන ‘සැෆිරස්’ යන ග්‍රීක වචනය මුල්කරගෙන බව පැවසේ. සබරගමු පළාතේ රත්නපුර, පැල්මඩුල්ල, කුරුවිට, බලංගොඩ ආදි ප්‍රදේශවල මැණික් බහුල වන අතර මේ හැර සිංහරාජ, මොරපිටිය, දෙණියාය, අකුරැස්ස, බුලත්සිංහල, හිනිදුම, ඇළහැර, ඔක්කම්පිටිය ප්‍රදේශ වලින්ද මැණික් හමුවෙයි.
ශ්‍රී ලංකාවේ මැණික් ගල් ප්‍රාග් කේම්බ්‍රීය යුගයේ හටගෙන ඇති බවට සැළකෙන අතර මෙරට මැණික් ප්‍රභේද හතලිහකට වැඩි ප්‍රමාණයක් ඇත. කොරන්ඩම් ඒ අතර හමුවන දීප්තිමත් වර්ණයන්ගෙන් යුත් මැණික් විශේෂයකි. පුෂ්පරාග මේ වර්ගයේ මැණිකක් වන අතර එය කහ වර්ණයෙන් යුක්ත වෙයි. ළා රෝස පැහැති පද්මරාග, නිල් හා රතු ආරුනූල් ද මේ වර්ගයේ මැණික් වෙයි. කනක නම් තවත් මැණික් වර්ගයක් මෙරටින් හමුවන අතර වෛරෝඩි, 
පසිංගල් මේ වර්ගයට අයත් වේ. මේවා ළා කොළ, තද කොළ පැහැයන්ගෙන් යුතු වෙයි. එසේම පදියං නැමැති මැණික් වර්ගයක් ලංකාවේ දක්නට ලැබෙන 
අතර කොළ, කහ, දුඹුරු හා ළා රතු පැහැති ජාගුන් නම් මැණික් වර්ගයද මෙරටින් හමු වෙයි. රබහ තවත් මැණික් විශේෂයක් වන අතර ඒවා ළා රත් පැහැයෙන් යුක්ත වේ. ගෝමේද මේ වර්ගයට අයත්වෙයි. පළිඟු නම් මැණික් වර්ගයක්ද වන අතර මේවා කහ, සුදු හා රෝස වර්ණයන්ගෙන් යුක්ත වේ. එසේම තෝරමල්ලි, පුන්ක්කන්,දියතරිප්පු, ලෙස තවත් මැණික් වර්ග ශ්‍රී ලංකාවේ දක්නට ලැබේ. නිල් මැණික්, රතු මැණික් හා වෛරෝඩි ශ්‍රී ලංකාවේ ඉහළ ඉල්ලූමක් ඇති මැණික් ගල් අතරට අයත් වේ.ස්වභාවිකව හමුවන මැණික් ඝර්ෂණයට හා ඛාදනයට ලක්වීමෙන් ඒවායේ ස්ඵටික ස්වභාවයෙන් ඈත් වී විෂමහාකාර හැඩවලින් යුක්ත වේ. එසේ නමුදු ඒවා කපා ඔප දැමීමෙන් එහි දිස්නය මෙන්ම වර්ණවත් බව ද වැඩි කළ හැකිය. මෙසේ සකස් කිරීමෙන් අනතුරුව ඒවාට ඉහළ වෙළෙඳ වටිනාකමක් හිමි වෙයි. මැණිකක් තක්සේරු කිරීමේදි භාවිත කරන ප්‍රධාන මිනුම් නම්, එහි පැහැයේ ගැඹුර, පිරිසිදු බව, පාරදෘෂ්‍ය බව, ප්‍රභාව හා පළුදුවලින් තොර බවයි. රත්රං මෙන්ම මැණික්වල බර මැනීමේදි ඉතා සංවේදි තරාදි භාවිත කරනු ලැබේ. මිනුම් ඒකක ලෙස ක්‍රාත් හෙවත් කැරට් යොදා ගනු ලබයි. ක්‍රාත් එකක් මිලිග්‍රෑම් 200කට සමාන වේ. මෙය අන්තර්ජාතික කිරුම් ඒකකය ලෙස භාවිතයට ගැනේ.
ශ්‍රී ලංකාවට විදේශ විනිමය ගෙනෙන දේ අතර මැණික් හා ස්වර්ණාභරණ කර්මාන්තය ප්‍රධාන තැනක් ගනී. මෙහිදි මැණික් ඉල්ලම් ප්‍රමාණය දිනෙන් දින අඩු වීම, ඉල්ලම් හෑරිමේ අපහසුතා, පහසුකම් අඩුවීම ආදිය නිසා අද වන විට ඉල්ලුමට සරිලන සැපයුමක් ලබාදීමට අපොහොසත්වන තත්ත්වයකට පත්වී ඇත. මීට අමතරව නිසි ක්‍රමවේදයකින් බැහැරව අවිධිමත් ලෙස සිදුකරන මැණික් පතල් හේතුවෙන් පරිසරය මෙන්ම මිනිස් ජීවිත විනාශ වූ අවස්ථාද බොහෝ දක්නට ලැබේ. තවද දැඩි අවදානම් මෙම මැණික් පතල් කර්මාන්නතයේ නියැලෙන්නන්ගේ ජීවිත සුරක්ෂිත කිරීමටද විශේෂ වැඩපිළිවෙලක් ක්‍රියාත්මක කළ යුතුව ඇත. එසේම මැණික් ඉල්ලම් සහිත ප්‍රදේශ
හඳුනාගැනීමේ ක්‍රමවේදයක් ඇති කළ යුතු කාලයද එළඹ ඇත. මේ අනුව මැණික් ඉල්ලම් බහුල ප්‍රදේශ පමණක් තෝරා ගනිමින් මෙම කර්මාන්තය සිදු කිරීමෙන් වෙනත් ප්‍රයෝජනයක් සඳහා ගත හැකිවීමට ඇති භූමිය විනාශ වීම මෙන්ම මුදල් නාස්තිය අවම කරගත හැකි වනු ඇත. කෙතරම් අලංකාර වුවද කෙතරම් වටිනා වුවද මෙරටට කෙතෙරම් විදේශ විනිමයක් රැස් කර දුන්නත් මේ හේතුවෙන් සිදුවන්නේ භූගත භූමිය කුහරයක් බවට පත්වීම පමණි.
මැණික් හැඳින්වීම
ශ්‍රී ලංකා ධරණි තලයෙන් මතු කර ගන්නා මැණික් ගල් වටිනා හා අර්ධ වටිනාකමකින් යුත් වශයෙන් වර්ග කළ හැකි අතර ''නිල් මැණික'' ශ්‍රී ලංකාවේ ජාතික පාෂාණය ලෙස ප්‍රකාශයට පත් කොට තිබේ.
නිෂ්පාදන
කොරන්ඩම් (කුරුවින්ද)
නිල් මැණික්, පුෂ්පරාග, රතු රෝස, සුදු නිල්, රත්න පුෂ්පරාග, නිල් ආර්නූල්, රතු මැණික්, රතු ආර්නූල්, පද්මරාග
නිල් මැණික්, පුෂ්පරාග, රතු රෝස, සුදු නිල්, රත්න පුෂ්පරාග, නිල් ආර්නූල්, රතු මැණික්, රතු ආර්නූල්, පද්මරාග
ක්‍රිසොබෙරිල්
කණක වෛරෝඩි, පසිංගල, පසිංගල් වෛරෝඩි, කණක
කණක වෛරෝඩි, පසිංගල, පසිංගල් වෛරෝඩි, කණක
ස්පයිනෙල් (කිරිංචි)
නිල් කිරිංචි, රතු කිරිංචි, දම් කිරිංචි
නිල් කිරිංචි, රතු කිරිංචි, දම් කිරිංචි
ටොපෑස් (පඩියන්)
සුදු පඩියන් (''ලන්ඩන් බ්ලූ'' බවට පරිවර්තනය කළ හැකි)
සුදු පඩියන් (''ලන්ඩන් බ්ලූ'' බවට පරිවර්තනය කළ හැකි)
සර්කොන් (ජාගුන්)
කොළ, කහ, දුඹුරු සහ අවර්ණ ජාගුන් (මාතර දියමන්ති)
කොළ, කහ, දුඹුරු සහ අවර්ණ ජාගුන් (මාතර දියමන්ති)
ගානට් (රබහ)
රෝස රබහ, ගෝමේද, රතු රබහ, මල් රබහ
රෝස රබහ, ගෝමේද, රතු රබහ, මල් රබහ
බෙරිල් (තරිප්පු)
තරිප්පු, හීලියෝඩර්
තරිප්පු, හීලියෝඩර්
ක්වාර්ට්ස් (පළිගු)
ස්මෝකි ක්වාර්ට්ස්, වයිට් ක්වාර්ට්ස්, අඹතේස්ත, ක්වාර්ට්ස් කැට්ස් අයි
ස්මෝකි ක්වාර්ට්ස්, වයිට් ක්වාර්ට්ස්, අඹතේස්ත, ක්වාර්ට්ස් කැට්ස් අයි
ටෝර්මලින් (තෝරමල්ලි)
දුඹුරු තෝරමල්ලි, කහ තෝරමල්ලි (දුඹුරු සහ කොළ තෝරමල්ලි)
දුඹුරු තෝරමල්ලි, කහ තෝරමල්ලි (දුඹුරු සහ කොළ තෝරමල්ලි)
ෆෙල්ඩ්ස්පාර්
චන්ද්‍රකාන්ති පාෂාණ
චන්ද්‍රකාන්ති පාෂාණ
දුලබ පාෂාණ
අඬලුසයිට්, කෝර්න‍‍රුපයින්, අගස්ති වර්ග, සිංහලයිට්, ලෝලයිට්, ඉන්ඩිකොලයිට්, ෆයිබ්‍රො‍ලයිට්, ට‍ාෆෙල්ටේ, එකනයිට්, ස්ටාර් ස්පයිනෙල්
මැණික්
විවිධ ප්‍රමාණයේ සහ ......................... මැණික් ගල්
මිමි අනුව සැකසූ මැණික් ගල්
දුලභ මැණික් වර්ග
මැණික් කැපීමේ සේවාවන්
විවිධ ප්‍රමාණයේ සහ ......................... මැණික් ගල්
මිමි අනුව සැකසූ මැණික් ගල්
දුලභ මැණික් වර්ග
මැණික් කැපීමේ සේවාවන්
සැපයුම් දාමය
- ශ්‍රී ලංකාව තුළ සිදු කෙරෙන කැණීම් ඔස්සේ ලබාගන්නා මැණික්
- ආනයනය කරනු ලබන මැණික්
ස්වර්ණාභරණ
කාන්තා හා පිරිමි අංශ සඳහා නිර්මාණය‍න් ශ්‍රී ලංකාව ලෝක ස්වර්ණභරණ වෙළෙඳපොළට ලබා දේ. ටයි කටු, ටයි ක්ලිප්, කමිස සඳහා අත් ගාංචු, කරාබු, මුදු, මාල පෙන්ඩන්ට්, අත් පළඳනා, ගෙළ පළඳනා සහ සාරි කටු මෙන්ම සුවිශේෂී ස්වර්ණාභරණ ප්‍රධාන තැනක් ගනී.
කැරට් 9, 14, 18 ප්‍රමාණ‍ෙය් රන්, ප්ලැටිනම්, රිදී හෝ ලෝහ වර්ග 2 හෝ ඊට වැඩි ගණනක සම්මිශ්‍රණයෙන් ස්වර්ණාභරණ නිෂ්පාදනය කෙරේ.
- වර්තමානයේදී ශ්‍රී ලංකාව ලෝක වෙළෙඳපොළෙහි උසස් තත්ත්වයේ නිල් මැණික් සපයන ප්‍රභවයක් වශයෙන්ද, කපා ඔප දැමූ, විවිධ ප්‍රමාණවල මෙන්ම හැඩතලයන්ගේ මැණික් සපයන්නෙකු ලෙසද සහ මෑතක සිට නවීන ස්වර්ණාභරණ සපයන්නෙකු වශයෙන්ද නමක් දිනා ඇත.
- තරුණ, දක්ෂතාවෙන් පිරිපුන් අභරණ නිර්මාණ ශිල්පීන්, නවීන නිෂ්පාදන පහසුකම් සහ මනා සේ පුහුණුව ලත් නිපැයුම්කරුවන් සිටීම මෙන්ම මෙම කර්මාන්තය තුළ සිටින විශේෂඥයින් විසින් නිරන්තරයෙන් පවත්වනු ලබන තත්ත්ව, මෝස්තර හා නිෂ්පාදන ක්‍රමවේදයන් දියුණු කිරීමට පවත්වනු ලබන සම්මන්ත්‍රණ හා වැඩමුළු නිසා ශ්‍රී ලාංකීය මැණික් ඉහළ තත්ත්වයෙන් අපනයන වෙළෙඳපොළට ලබාදීමට හැකිවී ඇත.
- සෑම අංශයකම මෝස්තර වැඩි දියුණු කිරීම ශ්‍රී ලාංකීය ස්වර්ණාභරණ නිෂ්පාදන කර්මාන්තයෙහි නිරන්තරයෙන් සිදුවන ක්‍රියාවලියක් වන අතර ක්ෂේත්‍රයේ විශේෂඥයින් විසින්, ස්වර්ණාභරණ වල තත්ත්වය වැඩි දියුණු කිරීම හා ඉහළ නැංවීම අරමුණු කොට ගත් වාර්ෂික වැඩමුළු සහ පුහුණු සැසි පවත්වනු ලැබේ.
- ශ්‍රී ලංකා අපනයන සංවර්ධන මණ්ඩලයේ සංවිධාන කාර්යයක් වන ''ශ්‍රී ලංකා ස්වර්ණාභරණ නිර්මාන සම්මානය'' හරහා නිපුණ වෘත්තිකයන්ට මෙන්ම හැකියාවෙන් පිරිපුන් ආධුනිකයින්ටද අන්තර්ජාතික ස්වර්ණාභරණ වෙළෙඳපොළට පිවිසීමට ඉඩ ප්‍රස්ථා ලබාදී ඇත.
- ස්වරණාභරණ කර්මාන්තය කෙරෙහි වන රජයේ ප්‍රතිපත්තිය ස්ථාවර හා දිරිගන්වන සුලු මට්ටමක පවතී. කර්මාන්තය සඳහා අවශ්‍ය අමුද්‍රව්‍ය හා ආශ්‍රිත ද්‍රව්‍ය, යන්ත්‍ර සූත්‍ර හා උපකරණ ආදිය ආනයනය කිරීමේදී ලිහිල් ප්‍රතිපත්ති අනුගමනය කෙරේ. මැණික් කර්මාන්තය සඳහා අවශ්‍ය ඔප නොදැමූ මැණික් වැඩි වශයෙන් ශ්‍රී ලංකාව වෙත ලැබීම සහතික කරනු වස්, ඒවා ආනයනය තීරු බද්දෙන් නිදහස් කොට තිබේ.
- මැණික් හා ස්වර්ණාභරණ හුවමාරු පොළ හරහා විශාල පරාසයක සේවාවන් එනම් වෙළඳ කටයුතු, මැණික් පර්යේෂණාගාර පහසුකම්, මැණික් සඳහා සහතික කිරීම්, අපනයන සේවා, ප්‍රවාහන සේවා හා නැව්ගත කිරීමේ සේවා, බැංකු හා රක්ෂණ පහසුකම්, ලෝහ පිරික්සුම් සේවා සහ ප්‍රමිති ල‍ාංඡන ලබාගැනීම වැනි සේවා මේ ඔස්සේ ලබා ගැනීමට ඉඩ ප්‍රස්ථා ලබාදී ඇත.
මෙහි සියලු කරුණු ජාතික මැණික් සහ ස්වර්ණාභරණ අධිකාරියේ වෙබ් අඩවියෙනි...
GEMSTONES FOUND IN SRI LANKA
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| Information about "Twelve Popular Gemstones from Sri Lanka" | ||||
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| 01. Corundum | ||||
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| 02. Chrysoberyl | ||||
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| 03. Spinel | ||||
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| 04. Topaz | ||||
| White Topaz | ||||
| 05. Beryl | ||||
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| 06. Zircon | ||||
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| 07. Garnet | ||||
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| 08. Tourmaline | ||||
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| 09. Quartz | ||||
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| 10. Feldspar | ||||
| Moonstone | ||||
| Not so common Varieties | ||||
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| Rare Gem Stones | ||||
SAPPHIRE
Blue corundum in all shades are identified as sapphires.
The reputation for producing the world’s best blue sapphire has shifted from time to time different localities like Kashmir in
These superior gemstones while carrying high price tags in international markets, also hold superlative positions among connoisseurs and those who seek the best. The most desired colour and tone for a sapphire has been described as an intense corn flower blue with a ‘velvety’ Iustre. The Combination of such features though rare, is the pride of this country. the colouring oxides responsible for this colour are basically iron and Titanium. Very often the colour pattern is in the form of regularly arranged colour bands alternative with the colourless, or it may be that the colour regions are irregular and patchy. In keeping with scientific phenomena, the colour concentration is high in the direction of the optic axis and as such, a crystal could display different shades of colour like palace blue, greenish blue and deep blue when viewed in different directions. These factors have to be taken into consideration when faceting. Blue sapphires of
Rubies
Corundum of a red colour are identified as rubies. Being corundum these have all the optical, physical and chemical properties of the mineral. These also have negligible quantities of chromic oxide in their compositions which do not in any way affect the general chemical formula. It is this element, chromic oxide which is responsible for the red colour of ruby. The colour in rubies could be in various shades and tones and is dependent on the quantity of chromic oxide present, its ratio in relation to other elements in the composition, and the nature of its distribution. The depth and intensity of color is related to these factors while the distribution of colour in ruby could be patchy, banded or uniform. The presence of chromic oxide in the correct proportions, in the desired quantities, in the correct manner of distribution within a glassy textured transparent body, free from flaws and inclusions produced the ruby of optimum quality. Such stones are most beautiful and are highly prized. In
Determining the possible locality of a ruby by colour and appearance alone would certainly lead to confusion and controversy. To eliminate such controversy other factors like mineral inclusions and twinning planes are of importance and should be taken into consideration. Rubies are generally sensitive to light purely because the sensitivity of the colouring element, chromium; and their luster appearance could differ according to the nature of the light under which they are observed. It is best that rubies are observed under natural daylight conditions, always remembering the fact that daylight conditions are different in different parts of the world; which factor could consequently creat a different colour sensation on the human eye.
A currently prevailing controversial question is ; where lies the demarcation line between the ruby as defined and the pink sapphire? Difference of opinion is rife. But sooner or later this issue has to be resolved. In this publication it is not intended to discuss this subject in detail. Nevertheless it is necessary to highlight a few vital and important opinions as put together by Widess (1981) in ‘Jewelers Circular Keystones: February 1981 ‘which are as follows;
The gemological Institute of America, “Only transparent corundum of medium light to dark tones of red to purple hues is properly called ruby. Very light tones of red are correctly called pink sapphires. Even some stones that are light rather than very light in tone are properly called pink sapphires. A very intense red colour is necessary to justifiy the use of thee term ruby’.
Peter T. Sciambra, Director, International Gemological Institute, “I.G.I.’ s definition is basically the same as that of the G. I. A. except that it leaves out the phrase ‘ a very intense red’ colour is necessary.”
Charles I. Carmona, Vice President, and Guild Laboratories “The guidelines for a ruby are very similar to G. I. A. except we add brownish red”.
Thomas E. Tashy Jr. (G. G.: F. G. A.) Director, Independent Gemological Laboratory says “We mostly adhere to the G. I. A. guidelines. We differ in very light stones which we call pink rubies instead of pink sapphires.”
David Widess (G. G.) of Widess & Sons, Los Angeles says “Any corundum of reddish hue no matter what lightness or intensity, tint, shade or tone shold be called a ruby.”
Dr Earl Anderson ph.D, President of the Gemological Research Group Inc. says that he is in “perfect agreement with and shares the opinion of David Widess” and goes on to say that any corundum of reddish hue no matter what lightness of intensity, tint, shade or tone should be called a ruby.”
Herbert Smith (1930) in his publication “Gemstones” states that “the tint of red stones (rubies) varies considerably in depth. Jewellers term them pink sapphires when pale but of course no sharp distinction can be drawn between them and rubies.’ Richard Hughes of the Asian Institute of Gemological Sciences after making reference to historical background explicitly states “In light of the strong historical evidence suggesting that the term ruby was originally understood to include all red to slightly bluish red corundum from the very lightest to deepest tones, A.I.G.S. is abandoning the use of pink sapphire as an individual variety of corundum. As of this moment we will no longer use the term, either in our educational programmes or on the gem identification reports issued by our laboratory.”
From all this the reader will realize the nature of the controversy. Even at present we are still grappling with this issue and what should be stated is, that this is not so much a scientific or a gemological problem. After all, this nomenclature is based on colour alone an as such the verdict is with the gem trading circles. There is reason to believe that
As a rule, ruby deposits as such have not been specifically localized in
the Embilipitiya- Uda- Walawe environs.
Pathmaraga
The term pathmaraga is a Sinhalese term applied to a very special colour variety of corundum, so named after the lotus flower as its colour is sometimes akin to a variety of this flower. This really is another variety of corundum where the distinct nomenclature is based on colour. This variety too has stirred up controversy regarding the understanding of the actual colour it displays. The pathmaraga has an exceptional colour combination which is very attractive and rare. The term pathmaraga is now a universally accepted varietal name. The colour combination produces the rare and beautiful colour of a sunset red at its best as seen across a tropical sky. In
Quite many dealers tend to misidentify and refer to brownish yellow sapphires, pale golden sapphires, deep golden yellow sapphires and also off pink sapphires as pathmaraga. This is by no means doing justice to this unique and beautiful gemstone. Pathmaraga corundum of a very good colour, good transparency and lustre, of reasonably good commercial and investment sizes, are available in
Pathmaraga could also be produced through a process of heat treatment technique of natural corundum conducive to such treatment and having the necessary special attributes. Here, evidently the colour producing elements (ingredients) are within the stone and the heating process activates these elements which in turn bring out and impart colour to the gemstone. The resultant colours are believed to be permanent. In relation to this a word of caution has to be added. These colours could also be achieved through a process of irradiation in which, colour permanency cannot be guaranteed. This could invariably dupe an unsuspecting and uninformed customer. Thus it may be that dealing in pathmaraga is more for the professional than for the novice.
Yellow sapphires: Golden sapphires: Orange sapphires
The sapphire, ruby and the pathmaraga of the corundum family have specific identifying names of their own whereas the other varieties (other than asteriated types) are all referred to as sapphires but with their respective colours prefixed, as has been mentioned earlier in this chapter.
Among yellow sapphires various shades are noted varying from pale yellow to saffron yellow and from yellow slightly tinted red to a deep citron yellow. Iron is basically the colouring element that is responsible for the colour. In local terminology the yellow sapphires are identified as 'pusparaga' Yellow sapphires are widespread and are found in all corundum producing areas, one of the most reputed areas being places around Aluthnuwara in the Balangoda region. Among allied colours are varieties identified as golden sapphire and orange sapphire. While the colouring elements are the same as in yellow sapphire, the golden sapphire is found to contain traces of chromic oxide as well, as revealed by the hand spectroscope (doublet at 6924 AO and 6928 AO). These colours are very much in demand and these are locally identified as 'ratnapusparaga.' These gemstones when perfectly transparent are extremely attractive.
The orange sapphire is yet another variety with a deep orange colour, the demand for which is now on the increase. These beautiful deep orange colours could also be produced by subjecting certain types of 'geuda' corundum to intense heat and these treated corundum are rather common.
The other colours in which corundum occur are green and its various shades (yellow green, bluish green) and purple, brown, pink and colourless. Green sapphire could be of an intense green colour but more often than not these carry a tinge of yellow which invariably display an inferior appearance. The bluish green varieties resemble aquamarIne in appearances.
The purple sapphire is always of a violet blue inclined to purple or rose red. It is a mixture of the colours red and blue and could sometimes resemble the colour of amethyst or that of a rose red garnet.
Yellow Sapphire from
Reference has already been made to pink sapphires under rubies and this variety will continue to be referred to as pink sapphires in this text, as the controversy is not yet resolved. Apart from these numerous colour varieties of corundum are also the colourless sapphires identified as white sapphires. When a single piece of corundum is found to have more than one colour, such stones are identified as parti-coloured sapphires. It is not surprising to find corundum having quite contrasting colours like blue and yellow, green and yellow or red and purple in a single specimen. Very often the colours are well demarcated but may sometimes merge into each other. 'Such bi-coloured gemstones are quite attractive when cut in numerous fancy shapes.
Star Sapphires, Star Rubbies and Cat’s Eyes from Sri Lanka
Asteriated Sapphires (Star rubies and star sapphires)
Among the corundum family are also asteriated rubies and sapphires as mentioned earlier. Asterism is a star like reflection effect caused by certain minerals within the host corundum. These are microscopic acicular mineral inclusions of special orientation. Very often these mineral inclusions are rutile (TiO2) in the form of crystallized needles. Asterism in corundum is more common and more effective than in most other minerals that do display this phenomenon. The inclusions are oriented within the stone in a particular relation to the vertical axis of the corundum crystal (c-axis). Such stones, when cut 'en cabochon', display a special reflection effect in the form of a six, or in rare instances a twelve rayed star on the cabochon surface. An interesting and common observation is, that in the case of a twelve rayed star, the 'silk' that produces it is bronze coloured causing a 'schiller' effect at the base of the stone. The asterism or the star effect is best highlighted when observed under an overhead light source. In this connection it is interesting to note the reference made by Paul Desautels of the Smithsonian Institute (1965) to a four starred sapphire in the Institute's collection. This gem is said to be from
Theoretically, asterism could occur in any colour variety of corundum but this phenomenon could be most highlighted and made conspicuous only in the colour varieties which could in effect create a colour contrast to the silvery reflection effect of the star. The ideal stone should also be semi-transparent, translucent or opaque. The star effect is most attractive in rubies and sapphires of darker hues. Asterism has also been seen in yellow and brownish yellow sapphires but the colour contrast is so little that the star effect is not prominent. In the ideal stones the rays should be properly centered showing uniformity of the angular intersections and the rays should be perfectly straight, each ray extending more than half way down towards the girdle and the individual rays narrowing to an end. The rays should be sharp and well defined, rather than being broad, and should merge imperceptibly into the stone. The rays should be perfectly white or silvery without being affected by the colour of the stone. The stones are best if these do not display colour banding or zoning when viewed from above. In some, immobile 'silk' (geuda) is seen as whitish patches scattered within the stone. These spoil the appearance of the stone. Accordingly a top quality stone will carry a sharply defined ray against a pleasing colour, and such stones are most favoured. The combination of such features are considered rare. Nevertheless,
Although certain rough material from certain localities in
It is said of asteriated corundum that, a combination of a perfect body colour, the ideal degree of transparency and a perfectly sharp and centered star is a rare occurrence in nature. A star sapphire of blue colour and of exquisite beauty from
'Geuda' corundum
On a varietal basis 'geuda' corundum is one of the more recently appreciated members of the corundum family. The origin of this peculiar sounding term is unknown although it has been in usage for quite a considerable period of time. Originally it was used to refer to a condition found in a gemstone which imparted to it cloudiness or a milky white opaline appearance both within and outside, (Gunaratne 1981). The term' geuda' was commonly used to describe a similar condition in any variety of gemstone and it is still so used. In relevance to this text and in keeping with the decisions taken at a national level symposium on Geuda sapphires the term' geuda' will be used only in relation to gemstones of the corundum group. In corundum, the cloudy, milky white opaline appearance is the result of a network of acicular mineral inclusions which are very often microscopic although sometimes visible to the unaided eye or with the help of a x 10 or x 15 loupe. This included mineral is primarily the element titanium in the form of rutile (TiO2) which has crystallized in the form of extremely fine needles occupying a position within the host crystal in relation to its structure. Rutile therefore is a guest mineral within the corundum host. This process has taken place during the crystallization of corundum. As mentioned earlier the titanium ion is an important and essential ingredient in imparting colour to corundum.
Although titanium is the principal element which causes the numerous shades of blue in sapphire it is also a proven fact that the contribution of iron towards this end is also important. As already stated, corundum in its purest form is seldom attained. It more often than not contains the metallic ions necessary to produce colour but owing to some phenomena these have failed to impart colour to the host mineral. Titanium is a colouring element that could produce widely divergent colours such as white and blue in all their allied shades. Titanium could occur free in nature or could enter into certain other minerals as inclusions. Titanium dioxide (rutile) within the corundum crystal could exist in any of the following ways:-
it could remain unabsorbed and exist within the stone as a mass of microscopically thin rutile crystals, producing a shimmering reflection effect commonly identified as 'silk' in gemmological jargon.
it could be partially absorbed and the presence of the rest is revealed by its misty, murky, opaline sheen sometimes associated with faint shades of blue.
it could be virtually absorbed into the corundum crystal and true to its form and function as a colouring agent impart colour to the host.
in still others, the microscopic network of needles could align themselves in relation to the crystallographic axis (c-axis) of the host mineral obeying certain crystallographic laws and could produce asterism.
Accordingly the impact of the presence of titanium in corundum is four fold: -
it displays a smoky murkiness with a milky sheen
it causes a shimmering reflection effect identified as 'silk'
it imparts colour
it produces asterism
Gubelin (1983) after his extensive researches in mineral inclusions has concluded that rutile in corundum could occur both syngenetically and epigenetically. It could logically be assumed that the origin of rutile in 'geuda' sapphires could be more of a syngenetic nature. For syngenetic rutile to occur within the corundum, two important conditions have to be fulfilled:-
the host should engulf a fair quantity of mother liquid rich in titanium and
be subject to rapid drop in temperature at least from the critical point at which crystallization of rutile commences.
The second condition could invariably arrest the optimum conditions in the process of crystallization of rutile and produce only very minute microscopic acicular rutile from a mother liquid rich in titanium. This arrested state could result in the production of misty, murky, silky corundum with or without a pale bluish-white milky colour. Evidently, herein we see that the cooling history of the mother liquid plays a vital role in the formation of ‘geuda' corundum in nature. Apparently, this arrested state has prevented the full development of the constituent titanium to produce and impart colour. The basic principle behind the heat treatment of 'geuda' is the possibility that this arrested process could be re-started if subject to a metamorphic phase in nature; or if subject to adequate temperatures under the required environmental conditions, in a laboratory.
Judging by its nature and appearance, 'geuda' corundum is of many types, and these when subject to intense heat, produce different results. On this aspect, much research has been, and, is being carried out. What follows is by no-means a resume on the subject of geuda corundum or heat treatment of geuda corundum, but merely an introduction to the newest variety addition to the corundum group of gemstones.
It is thought that of all the corundum mined in
The treatable geuda sapphires of
Accordingly, the symposium classification identified four main sub-varieties, which names were already in common usage in the trade. What the symposium did was to specifically categorize and separately identify the numerous varieties according to their properties as follows: - ‘diesel geuda', 'silky geuda', 'ottu geuda' and 'dhun geuda'. The symposium also provided information about the techniques of treatment to be adopted for the different sub-varieties of geuda.
Sri Lankan gemstones of the corundum group in foreign collections:
Source: Colour Encyclopedia of Gemstones: Joel Arem (1977)
Gems of the Smithsonian Institution: Paul E. Desautels (1965)
Gemstones: Herbert Smith (1972)
(1) Pathmaraga: 28.6 carats: Royal Ontario Museum, Canada.
(2) Pathmaraga: 100 carats: American Museum of Natural History.
(3) Yellow Sapphire: 100 carats; American Museum of Natural History
(4) Yellow-brown sapphire: 35.4 carats: Smithsonian Institute, Washington
D.C.
(5) Yellow-orange sapphire: 22 carats: Smithsonian Institute, Washington
D.C.
(6) Golden-yellow sapphire: 179.4 carats: Royal Ontario Museum, Canada
(7) Greenish-yellow sapphire: 43.95 carats: Royal Ontario Museum, Canada.
(8) Orange sapphire: 31 carats: Smithsonian Institute, Washington D.C.
(9) Colourless sapphire: 25.3 carats: Smithsonian Institute, Washington D.C.
(10) Colourless sapphire: 16 carats: Smithsonian Institute, Washington D.C.
(11) Purple sapphire: 42 carats: Smithsonian Institute, Washington D.C.
(12) Blue-sapphire: 163 carats: Pierpont Morgan Collection, American Museum
of Natural History.
(13) "Star of India" (blue) : 563 carats: American Museum of Natural History
(14) "Midnight Star" (deep purple) : 116 carats: American Museum of Natural
History.
(15) Rosser Reeves Star Ruby: 138.7 carats: Smithsonian Institute, Washington
D.C.
(16) Logan sapphire (blue) : 423 carats: Smithsonian Institute, Washington D.C.
(17) "Star of Artaban" (blue) : 316 carats: Smithsonian Institute, Washington
D.C.
CHRYSOBERYL
As a group of precious gemstones Chrysoberyl is known to occur as three distinct varieties namely Chrysoberyl, alexandrite and cymophane. All varieties are chemically identical, being an aluminate of beryllium (Beryllium alluminium oxide – BeAl2O4 ) although distinctly dissimilar in appearance. Being an all chromatic mineral, in its purest form, it would be colourless; Chrysoberyl are by no means rare. Very often the different varieties have ferric oxide and chormic oxide as colouring element “impurities”. As in corundum these colouring elements do not in any way affect the chemical formula, as the quantities are so negligible. Approximately the alumina content is as 80% and the beryllia content rarely exceeds 20%.
Chrysoberyl crystallizes in the orthorhombic system, the crystals invariably occurring as inter- penetrant complex twin crystals, and as such simple individual crystals are rare. The mineral has a hardness of 8.5 on Moh’s scale and because of this superior hardness it could take and retain a brilliant polish. It is doubly refractive and its refractive indices are 1.745-1.754 and its birefringence could vary between 0.008 and 0.010. The different colours and varieties could however show slight variations in these properties. Certain alexandrites from
In
“Chrysoberyl mined from the pegmatite is transparent, apple green in colur, and varies in size from 1mm. to 8mm. Some worked specimens displayed chatoyancy while a few possessed sufficient colour change to be termed as alexanadriete.” The extent and the potential of this occurrence is not as yet known and await further surveys but activity is brisk.
Chrysoberyl
Quite unlike corundum, Chrysoberyl occurs only in a few colours, the common colours being yellow, golden yellow, brownish yellow, yellowish green, bluish green and faint olive green.Chrysoberyl occurs in varying degrees of transparency ranging from transparent and clear to cloudy translucent and opaque.
The classification of chrysoberyl into varieties depends on colour, colour changing properties, inclusions and reflection effects these could produce.
Gem quality chrysoberyl is generally transparent and when polished makes beautiful gemstones. The golden yellow and the green varieties are much favoured and are in demand. Stones of considerably big sizes are not uncommon in
Cymophane – Chrysoberyl Cat’s eye:
A variety of chrysoberyl with acicular mineral inclusions oriented in relation to the vertical axis of the chrysoberyl crystal structure capable of producing chatoyancy is identified as cymophane. In its structure these innumerable microscopic needle like inclusions create a silky reflection effect. The solid mineral inclusions some times may not be present but the hollows or tubes that once contained these could produce the same effect. These generally are positioned in a direction along the vertical axis of the crystal, or in the alternative it could be a multitude of relatively short needles of mineral inclusions arranged in a manner vertical to the c-axis (W.F. Eppler - as recorded by Webster 1983). These inclusions make stones cloudy, reduce transparency and produce reflection effects. These if properly oriented would, when cut 'en cabochon' display chatoyancy, or the cat's eye effect. What is produced is a silvery streak of light which is displayed across the cabochon surface. This has a striking resemblance to the pupil of a cat's eye. Chatoyancy, like asterism is a reflection effect brought about by the stone's inclusions and its effect is determined by the nature of the stone. This effect could be either enhanced or diminished by the lapidary by varying the curvature of the cabochon and the spread of the cabochon surface. After a research study of chatoyancy in chrysoberyl cat's eyes from
The silvery streak of light could be very sharp or diffused. Generally this streak of light will be well defined in smaller stones in the sense that their boundaries could be sharp and distinct. In the larger stones this effect has a tendency to be blurred and indistinct sometimes gradually merging into the body colour of the stone. This does not in any way mean that the bigger stones are inferior or not as effective. This is a very generalized statement as extremely attractive large sized stones are a special feature of the Sri Lankan types. Characteristically cat's eyes are cloudy and translucent, which factors, heighten the effect of chatoyancy. In clear and transparent stones the effect is considerably reduced.
The value of cat's eye will depend on the effectiveness of the ray, the size of the stone and the colour. Some common colours in which cat's eyes occur are milkywhite to grey, bluish or greenish-white, apple-green, greenish-yellow, honey-yellow, brownish-yellow and brown grading into black. Black is extremely beautiful when coupled with a sharp silvery ray across it. Honey coloured stones are much in favour but this could change with fashion trends. Certain stones show bi-colour effects or shades appearing on either side of the ray, and sometimes the ray seems split when observed from a certain distance from the light source but, would join up at an optimum distance. Mullenmeister (1980) has recorded the discovery of a white chrysoberyl variety from
Six rayed star chrysoberyls are also met with but rarely, the cause of which is once again inclusions. The stones have to be cut 'en-cabochon' to display the effect.
Cat's Eye
Alexandrite:
The term alexandrite is applicable to the dark grass green, emerald green and bluish green varieties of chrysoberyl where the colours are attributed to the presence of chromic oxide in the composition. Chromic oxide in fact occurs as a trace element in the composition in negligible quantities and it is the presence of this element that helps in differentiating alexandrite from chrysoberyl. This means that for a chrysoberyl to be classified as an alexandrite, it should invariably have chromic oxide, the presence of which could be easily detected with the help of a spectroscope. Further, a simple visual observation to distinguish between alexandrite and chrysoberyl is to note its apparent phenomenon of showing a colour difference when observed under artificial light. In alexandrites the colour changes from green or bluish green in daylight to varying shades of raspberry red under artificial incandescent light. The colour under artificial light is usually inclined to violet. In some the overall effect could be very conspicuous while in others it could be less and in still others it could only be faintly apparent. However, it should be borne in mind that an apparent colour change could also be the effect of almost invisible brownish stains in the stones caused by iron. The only positive method by which to determine the difference is with the help of the spectroscope. This instrument will reveal the presence of chromic oxide if present by displaying a strong absorption doublet in the deep red end at 6803 Ao and weaker lines at 6650 Ao, 6550 Ao and 6450 Ao (Anderson, 1971). In certain instances reddish tints are quite visibly observed in normal daylight conditions as well. In such cases the colour change effect will quite naturally be enhanced under artificial light. By virtue of this colour change alone, these cannot, and should not, be identified as alexandrite unless the presence of chromic oxide is revealed on examination.
By way of a comparison a reference is made to alexandrite from Tanzania "which displays a blue green in white fluorescent light, rich green in daylight and a reddish violet with bluish overtones under incandescent light" (Dunn 1976).
Generally the average gem dealer is in the habit of identifying alexandrite only by the nature of the colour change. This would be extremely misleading as already mentioned since the presence of iron stains could produce a similar result. On the other hand it is well to remember that even if the stone does contain chromic oxide to fulfil the scientific classification requirement the expected colour change under artificial light could be extremely faint or hardly visible. The market potential of such material would be much less. The colours and colour change intensities could be of different degrees in different stones. This apparently is directly related to the amount and ratio of chromic oxide in relation to the other elements that are present in the composition. The colour-quality of alexandrite is judged by the nature and distribution of the original colour and the intensity of the colour change in artificial light. Accordingly the best quality alexandrite should be perfectly green or bluish green in daylight, changing to a raspberry red inclined to violet under artificial incandescent light.
Alexandrite is essentially a facettable gemstone but certain stones from
Generally large clear and flawless alexandrites are hard to come by. Good stones of appeal are extremely rare.
An alexandrite of superlative quality is a gemstone of very rare occurrence and the countries known to produce such material are very limited. Apart from
It might perhaps interest the reader to note that alexandrite was discovered in the
Gemstones of the Chrysoberyl group from
Source: Colour Encyclopedia of Gemstones, Joel Arem. (1977)
Gems of the Smithsonian Institution: Paul E. Desautels (1966)
(1) "Hope Chrysoberyl" : 45 carats:
(2) Cat's eye: 29.4 carats (yellow green):
(3) Chrysoberyl: 42.72 carats (green):
(4) Cat's eye: 171 carats (gray-green): Smithsonian Institute, Washington
D.C.
(5) Cat's eye: 47.8 carats: Smithsonian Institute,
(6) Cat;s eye "The Maharani" : 121 carats: Smithsonian Institute, Washington
D.C.
(7) Chrysoberyl : 114.3 carats: (yellow-green) : Smithsonian Institute,
(8) Chrysoberyl : 120.5 carats: (green) : Smithsonian Institute, Washington
D.C.
(9) Chrysoberyl : 31.7 carats (brown) : Smithsonian Institute,
(10) Cat's eye: 147.7 carats: (chartreuse - apple green) : Crown Jewels of
(11) Alexandrite: 65.7 carats: Smithsonian Institute,
(12) Alexandrite: 16.7 carats: Smithsonian Institute,
(13) Alexandrite: 11 carats: Smithsonian Institute,
SPINEL
Spinel is a gemstone found in greater abundance in Sri Lanka than either corundum or chrysoberyl. Its very abundance makes Sri Lanka the second largest producer of this stone next to Myanmar (Burma). Spinel is found in association with other varieties of gemstones among the gem gravels of this country. These are more closely associated with corundum, being found in the same environment and being deposited in much the same manner. These also show similar colour resemblances to the corundum varieties particularly in respect of red, orangish red, blue, mauve and the colourless. Nevertheless these arc two distinctly different mineral groups.
Chemically, spinel is an oxide of aluminium and magnesium and belongs to an isomorphous group, where a certain amount of ferrous, manganous or zinc oxide could replace some of its magnesia, while ferric or chromic oxide could replace some of the alumina. Because of this isomorphous replacement its composition varies slightly. Consequent to this variation in its chemistry, slight differences in their optical and physical properties are seen in the different varieties. Spinel crystallizes in the cubic system and its most common crystal habit is octahedral. These have a specific gravity that varies between 3.60 and 3.63 and a refractive index which varies between 1.710 and 1.717 for the gem varieties. Apart from the common varieties of spinel are also varieties identified as Ceylonite, Gahnite and Ghanospinel. These varieties because of their differences in composition which is the result of isomorphous replacement have much higher readings in their optical and physical 'constants' such as specific gravity and refractive index.
Spinel
Ceylonite:
Ceylonite is a magnesium iron aluminium oxide (Mg1 Fe, Al2 O4). This variety has been quite rightly named after Sri Lanka (Ceylon) in view of its reputation for this variety of spinel. It is an iron rich variety which is of a very dark green, grading to dark greenish-black or black. The black varieties are opaque and are of very little significance as gemstones. Nevertheless these could take a very good polish and are then attractive in their own way and could be used in modern jewellery settings. Ceylonite is found as waterworn pebbles among the gem gravels of this country. These have a refractive index that varies between 1.77 and 1.78 and a density within the range of 3.63 and 3.90.
Gahnite:
Gahnite is a zinc aluminium oxide and rich in zinc. These stones are green in colour and transparent materials when facetted are attractive. This material has been so named after its discoverer G.J. Gahn a Swedish chemist These have very high densities recording a range between 4.0 and 4.62 and a refractive index around 1.805. However the Nigerian varieties as recorded by Jackson (1982) are said to have a refractive index ranging between 1.793 and 1.794 and a density varying between 4.400 and 4.589. This could be attributed to the varying percentages of zinc in the composition.
Ghanospinel :
Ghanospinel is a magnesium zinc aluminium oxide occurring normally in very dark colours - dark blue and bluish black. It could be said that this variety is invariably found among the gem gravels of Sri Lanka. It has a density that varies within a wide range between 3.58 and 4.06. Its refractive index also varies between 1.725 and 1.753. An interesting revelation has been made through the researches of Anderson (1964). Accordingly, certain light blue spinels which apparently gave no indication of excessive iron, and displayed a normal appearance were found to have very high densities and refractive indices. The crux of the revelation was that the presence of zinc was the cause. Most of the test samples were blue spinels from Sri Lanka. The conclusion arrived at thereby was that certain blue spinels of pale colour and normal appearance from Sri Lanka could have surprisingly high densities and optics suggesting the presence of zinc. Further reference has been made to this by Anderson (1974). A reference has also been made to a ghanospinel octahedron crystal from Ratnapura weighing 4.3 grams (Frenzel etal 1986).
Recent research by Schmetzer and Bank (1986) shows that colour absorption spectra, and inclusions in zinc-bearing ghanospinel were found to be similar to the properties of ordinary zinc free spinel from Sri Lanka.
The colours in which spinel occurs are red, pink, orange, shades of reddish-purple, blue, bluish-green, mauve and colourless. Ceylonite is usually greenish black to black in colour and is almost opaque. Spinel occurs in varying degrees of transparency ranging from transparent to opaque. The cause of colour in spinel is the colouring ions chromium in the reds, ferrous iron or cobalt in the blues and allied shades, and manganese in the purple stones. The occurrence of natural blue spinel coloured by cobalt has been found in Sri Lanka. This refutes the original theory that only synthetic stones had cobalt as their colouring agent and that the presence of cobalt was conclusive enough to declare such stones as synthetic productions. However, beautiful natural blue spinel coloured with cobalt are now available. Harder (1986) has recorded that cobalt bearing spinel having traces of iron, nickel, vanadium and gallium has been found in the gem gravels around Paradise Estate mining area in the vicinity of Ratnapura. Cobalt spinel has also been found around Okkampitiya and Embilipitiya
Spinel has a hardness of 8, occupying the fourth place in Mohs's scale of hardness. Being hard, spinel is able to lend itself to a high degree of polish. The red and reddish purple stones show colour resemblances to rubies and garnets but are easily differentiated. Large, fine gem quality spinel exceeding 10 carats are rare. Blue spinel is somewhat more abundant, and beautiful dark blue stones of a good lustre are not uncommon. Of the more common colours are blues slightly inclined to purple, mauve, brownish-red and greenish-blue stones, while colourless stones do occur but are rare.
Asteriated spinel with either four or six rays are also found in the gravels of Sri Lanka. Generally a majority of asteriated spinel are of bluish or brownish-red and purplish-red colours. The cause of asterism is the same as in the case of corundum, being a reflection effect off inclusions. Investigations of Bank (1980) have revealed that the inclusions causing this star effect are rutile needles. He also states that for the first time star spinel from Sri Lanka were obtained in 1979.
Synthetic spinels that compare very closely to their natural counterparts are being manufactured. However, their optical behavior and their physical characteristics differ and this makes detection easy.
Colour changing 'alexandrite-like' spinel have also been found from time to time in this country. Here the original colours are quite different to alexandrite, very often being violet in daylight and changing to reddish violet in incandescent light. An analysis of such material by Schmetzer and Gubelin (1980) has revealed the composition to be iron, chromium and vanadium. Colour changing blue spinels have also been found recently in this country among its gem gravels. The colour changes to a purplish shade under incandescent light.
A deep red to black manganese aluminum oxide variety identified as galaxite is not known to occur in Sri Lanka but mentioned here as information. These have a very high refractive index around 1.92 and a density of around 4.05.
Sri Lankan Spinel in foreign collections:
Source: Colour Encyclopedia of Gemstones: Joel Arem (1977)
Gems of the Smithsonian Institution: Paul E. Desautels (1965)
(1) Pale purple spinel: 45.8 carats: Smithsonian Institute, Washington D.C.
(2) Pink-violet spinel: 29.7 carats: Smithsonian Institute, Washington D.C.
(3) Red Spinel: 71.5 carats: American Museum of Natural History
(4) Blue-violet Spinel: 22 carats, Smithsonian Institute, Washington D.C.
(5) Rose-brown Spinel: 22 carats: Smithsonian Institute, Washington D.C.
GARNET
Garnets are a group of minerals, the varieties of which have complex chemical compositions. These are of an isomorphous series, the constituent elements of which are capable of replacing each other to a remarkable degree. The chemistry of this group of minerals is quite interesting to the gemmologists and mineralogists alike in that elements like calcium, magnesium and iron (ferric), manganese and chromic oxide could replace each other in certain proportions without creating a change in the crystal form. This isomorphous replacement as it is called has caused the intermixture of chemical compositions and created distinct different varieties and colours. Nevertheless these varieties are not compartmentalized or water tight. There is gradual merging of elements from one into the other in certain ratios, which factor could also create intermediate varieties. In other words the composition of one gradually merges into the other. On a chemical basis garnets are divided into different varieties and the divisions are not sharply demarcated. As early as 1964 Anderson has noted that the intermixture of elements are mainly confined to certain varieties which he has classified under two distinct divisions, the pyralspite and ugrandite series. In the pyralspite series are the varieties pyrope, almandine and spessartite and in the ugrandite series are uvarovite, grossular and andradite varieties. Accordingly, for gemmological purposes garnets are discussed under these main varieties:-
(i) Pyrope - Magnesium aluminium garnet
(ii) Almandine - Iron aluminium garnet
(iii) Spessartite - Manganese aluminium garnet
(iv) Uvarovite - Calcium chromium garnet
(v) Grossular - Calcium aluminum garnet
(vi) Andradite - Calcium iron garnet
Of these varieties andradite and uvarovite have not been found to occur in Sri Lanka and also the beautiful green grossular coloured by chromic oxide, marketed as tsavorite.
All varieties of garnet crystallize in the cubic system (isotropic). Garnets are of common occurrence. The superior gem quality varieties are beautiful and attractive enough to be set in very costly jewellery. Garnet is a commonly associated mineral constituent of the khondalite group of rocks of this country and as such it is quite widespread. In fact, it is an essential and more common alternative constituent to corundum in the rock types of the khondalite group. Garnets are mostly obtained from among the alluvial gravels and also from the weathered 'in situ' occurrences. As in other gem minerals garnets too occur in varying degrees of transparency, the fully transparent ones with good colour being the most beautiful. They could also display asterism in the form of a four rayed star. Even chatoyancy has been noted from among the Sri Lankan material as has been established by some brownish red cat's eyes brought to the State Gem Corporation sometime ago for export. Their examination revealed these to be garnets with microscopic inclusions which produced chatoyancy. Their most convincing diagnostic feature was the typical absorption spectrum, and the stones were singly refractive. The stones were pyrope - almandine garnets. This is probably the first such instance to be recorded. All chatoyant and asteriated garnets apparently have been of this variety.
The value of a garnet as a gemstone depends on the depth and intensity of colour, its lustre, clarity and transparency and its flawlessness. Different varieties of garnets have different properties and these will be discussed separately. Garnets are idiochromatic and as such the different colours are caused by elements such as iron, manganese, chromium, calcium, and magnesium which are essential constituent elements in the composition of the respective varieties. As a rule uniformity of colour is observed in all garnets. Red and its diverse shades are the commonest colours in which the varieties, pyrope and almandine occur. These colours are very often tinged with brown, yellow or violet. The red could sometimes be so intense as to appear black and opaque. However the smaller pieces show the colour very distinctly. The beautiful purplish tinted garnets which are fairly abundant in the Matale-Elahera regions are really an intermediate variety between pyrope and almandine. The term pyrandine has been suggested by Anderson (1974) for this intermediate type, but this term has not been favourably accepted. The term rhodolite seems to be the more acceptable term probably because of its rhododendron-red colour. Further, it sounds better as a trade name. This intermediate type of garnet is mostly confined to the Elahera regions. Here the colours are extremely fine, the stones clear and transparent and what is more are found in reasonably large sizes. The superior quality of this variety from this region is so renowned that these are sometimes identified as 'Elahera garnets' in order to make the variety more specific. Generally, the pale yellow and yellowish colours, and the orange and deep orange colours are of the varieties hessonite and spessartite respectively.
(i) Pyrope:
Pyrope is essentially a magnesium aluminium garnet with varying amounts of iron, manganese and chromium in the composition as replacement elements. This variety is of a deep rich blood red colour, the colour of which is attributed jointly to the presence of iron, manganese and chromium. The overall colour is invariably associated with a tinge of yellow. Certain colours in pyrope garnets match closely the colours of rubies and these ruby red garnets are much favoured. An exceptional feature about pyrope is that in comparison to other varieties, these are less impaired by cracks and fissures. Pure pyrope is less abundant in this county although it could be said that it is more widespread in occurrence being found in many areas. Nevertheless, one observes a greater output from areas around the Embilipitiya Uda- Walawe regions.
The refractive index of this material varies between 1.73 and 1.77 while its density could also vary between 3.7 and 3.8. Its hardness is 7 in Mohs's scale.
Magnesium and aluminium are not known to impart colour to minerals. Therefore quite logically pure pyrope should be colourless, but pyrope in the colourless state is hardly seen, because iron, manganese and chromium are invariably present in the composition as a result of isomorphous replacement.
Garnet Red Mauve
(ii) Almandine:
Almandine is an iron aluminium garnet which also contains ferrous and manganous oxide - the pyrope and spessartite molecules respectively, being the result of isomorphism.
The specific gravity (density) of almandine varies between 3.90 and 4.30. Its refractive index lies between 1.77 and 1.81. This variation is attributed to variable quantities of iron in the composition. It has a hardness of 7.5 in Mohs's scale. Almandine normally assumes a very dark deep red colour or crimson colour, often tinged with violet but it could also occur in varying shades. The colour is due to the presence of iron in its composition and occasionally the stones are so dark that it even hinders transparency. This is the reason why, old cabochon cut almandine garnets were hollowed out at the base in order to reduce their colour intensity, and thereby increase transparency. These have been referred to as 'carbuncles' in old literature. The other colours of almandine vary between brownish-red and reddishbrown and black and the stones occur in varying degrees of transparency. Even though almandine is found in fair abundance in this country, most of the materials are mixtures of.almandine and pyrope, more correctly referred to as almandinepyrope garnets. Very often this variety is impaired by cracks and fissures in their natural state. As referred to earlier, an intermediate variety between almandine and pyrope which strictly cannot be considered as an iron aluminium garnet nor a magnesium aluminium garnet is identified as rhodolite. In appearance it differs from both almandine and pyrope in respect of colour which is a beautiful violet. Martin (1970)after a detailed study of rhodolite garnet states that the "refractive index lies within the range for pyrope, yet the stone is of an entirely different colour, rose red to pale violet, while spectroscopy reveals the three main absorption bands of almandine and these are of moderate intensity." Lankan rhodolite is superior in respect of transparency, colour and size. It has an approximate density of 3.82 and a refractive index of 1.76.
(iii) Spessartite:
Spessartite is the manganese aluminium variety of garnet. It also has iron in variable quantities which very often replaces a little of the manganese molecule in the composition. These stones are generally of a brownish-red colour, reddishorange, or even reddish inclined to violet and yellow. The colour is invariably due to manganese and iron, manganese being the predominant colouring agent. The deeper colours of hessonite in which the manganese ratios are high could sometimes resemble spessartite. Compared to hessonite, spessartite is free from flaws and clean specimens are very attractive. This simple observation at times helps in distinguishing between these two varieties. Large transparent stones are rare. Yet, splendid stones are found among the gem gravels of Sri Lanka making Sri Lanka a major source for good quality spessartite. The refractive index is about 1.81. It has a hardness of 7.25 in Mohs's scale and its density varies between 4.1 and 4.3.
Spessartite
(iv) Hessonite: (Grossular)
Chemically hessonite is a calcium aluminium garnet mixed with small quantities of ferrous and manganous oxides which are replacement elements in the composition. But for these replacement elements hessonite would be colourless. The common colours of hessonite are pale yellow, yellow and brownish-yellow and these colours are inclined to orange or honey yellow. The intensity of the colour could vary depending on the degree of replacement. The gem varieties are generally transparent. Characteristically hessonite has a 'treacly' texture which hinders full transparency to some extent. This 'treacly' texture in hessonite is very characteristic and could even be an identifying feature. Further, hessonite as a variety is invariably impaired by minute cracks and fissures in addition to numerous inclusions and the Sri Lankan varieties are no exception, except in extremely rare instances. Such perfect pieces are very beautiful and make very good ornamental stones. A generally prevailing belief among certain folks is that hessonite has the power of warding off malefic influences and as such the wearer of hessonite would be comparatively free of being thus affected. Hessonite is confined mostly to the southern regions of the country and are mostly found in weathered' in situ' occurrences around Kamburupitiya in the Matara district. Hessonite is also found as rounded water worn pebbles among the gem gravels, in these regions.
As the variety spessartite too, occurs in deep golden yellow and yellow brown colours these could be mistaken for hessonite. Such colours in hessonite could be due to the corresponding increase of manganese in hessonite before finally grading into the spessartite variety. Hessonite has a hardness of 7.25 on Mohs's scale. Its density is around 3.65 and its refractive index lies between 1.742 and 1.748. It has been noted that in quite transparent varieties these properties are fairly constant at 1.743 (RI) and 3.65 (density). Sri Lanka is a major source for hessonite garnets.
Hessonite
Colour changing Garnet:
Apart from what has been already described, colour changing 'alexandrite type' garnets have also been found to occur among this country's gem gravels. These are of a brownish-green colour in appearance under normal daylight but show a significant colour change when observed under artificial incandescent light. Under artificial light these change into a beautiful violet or raspberry red as seen in alexandrite. It is most likely that chromic oxide is responsible for this phenomenon. However, the following analysis should be interesting to note. A similar colour changing garnet from Tanzania has been analyzed by Crowningshield (1970), and the analysis has shown that it had 0.54% of chromium, 0.32% vanadium and 0.1418% titanium. It was considered that vanadium was the cause of this colour change. Its refractive indices, density and hardness fall within the range for pyrope garnet.
Consequent to a study made on a colour changing garnet from East Africa (which could also perhaps be a test sample from Tanzania or Kenya) Jobbins et. al (1975) reported that the test sample was greenish blue in daylight and turned into a distinct magenta under incandescent light. Its readings were close to the pyrope range. It was further stated that "no chromium was indicated in the absorption spectrum". Their conclusion was that the influences of chromium on the colour changes are minimal if any, and they ascribe the colour change to vanadium in the composition. However, according to Crowingshield's analysis it is quite apparent that certain colour changing garnets do contain chromic oxide. In such instances at least the influence of chromic oxide on the colour and the colour change effect could not possibly be ruled out. Since these are essentially pyrope-spessartine garnets and since their physical and optical properties are closer to and within the range of pyrope garnet, which has a variable percentage of chromic oxide in its composition as a replacement element; it remains a matter for consideration.
Sri Lankan Garnets in foreign collections:-
Source : Gems in the Smithsonian Institute, Paul E. Desautels (1965)
(1) Garnet - Orange brown, 64 carats, Smithsonian Institute, Washington D.C.
Garnet Rose
Tourmaline
The term Tourmaline has been apparently derived from the Sinhalese term “Thoramalli”. As for the origin of the term “Thoramalli” itself, a very plausible explanation among the local people is that it bears the identical colour resemblance to the flower of a common wild plant, identified as “thora”. The flowers of these plants are yellow and has a brown calyx which covers about one third of the flower giving an overall yellowish – brown appearance. It could be said that this colour matches perfectly the colour of s yellowish – brown tourmaline, The yellowish brown tourmaline are more abundant in Sri Lanka compared to other colour varieties. As Sri Lanka has a reputation for the brownish yellow tourmaline it is possible that the term tourmaline is a combination of the Sinhalese term ‘ thora.’, the name of the plant and ‘mal’ the Sinhalese term for flower (thora-mal).
In
Tourmalines are an ismorphous group of minerals and their chemical composition is very complex and variable. It is so complex that it is difficult to describe it under a general formula. It is a silicate of born and aluminium and there are always present in all varieties of tourmaline other elements like magnesium, sodium, potassium and water. Flurine, Lithium and manganese enter into the composition of a few while the presence of the amount of iron is variable though important. Analyses have revaled that the silica- boron ratio is fairly constant while great variations are seen in the ratios of other constituents. These variations in the composition cause differences in colour, degrees of transparency and slight differences in the optical and physical properties like, refractive indices, density and hardness. The refractive indices within the tourmaline group could vary between 1.62 and 1.65, the density between 3.00 and 3.2 and its hardness could vary between 7 and 7.5. It is interesting to note that inspite of such chemical, optical and physical diversity which gives rise to different varieties of a range of different colours, tourmaline as a group crystallizes in the trigonal system. The crystals are characterized by vertical striations along their prism lengths. Corresponding to the complexities of composition the varietal classification of tourmaline is a very complex one. The classification becomes even more complex when one observes a further classification of tourmaline in relation to colours in which they occur, and which also corresponds closely to the composition. On the basis of the composition of tourmaline and the colours these display, distinct varieties are identified, in relation to both, for scientific and trade purposes, as follows : Dravite, Uvaite, Liddicolite, Elbaite, Rubellite, Siberite, Indicolite, Tsilaisite, Schorl and Achroite. The various colours in which tourmaline occur are due to the basic and essential ingredients in their composition. Tourmalines are found in varying degrees of transparency and these are highly dichroic.Dichroism is most apparent in dark colours which could even completely impair the passage of light in certain directions. Among tourmalines are quite a range of colour varieties. Those of good and pleasing shades of colour, sufficiently transparent and flawless are fashioned as gemstones. In respect of colour it is seen that certain crystals are parti- coloured having more than one colour in them, different portion being of different colours. The different colours could be seen along the length of the crystal and here the colours are at the two ends where the colour demarcations are very abrupt and sharp. Sometimes colour zoning is seen in a concentric arrangement. This is most apparent if the crystal is sliced in a direction perpendicular to the vertical axis. Then it will be seen that the core is differently coloured to the periphery and sometimes there is a lighter shade of colour in between as well. Mitchell (1984) describes this feature thus: “crystals can vary in colour concentrically around the c- axis or even vary in colour along the length of the crystal.” Those tourmalines with concentric zoning of colour are referred to as ‘watermelon’ tourmaline. Very often the colours are red and green. Michel (1984) however continues further by making reference to his own collection of parti- coloured tourmaline sighting samples that have the colours, yellow and green, gray and red and blue and pale yellow. He also makes an interesting reference to a specimen in his collection which is red and green chatoyant tourmaline, which indeed is a rare occurrence. Material with concentric zoning of colours has as yet not been recorded from
Tourmalines that are of a shade of blue are termed indicolite. These could be either dark or light in colour or could be of an indigo blue colour which apparently has given it its name. These very often reveal a tinge of green when closely observed. Deep indigo blue varieties of good transparency are highly prized, for such colours with perfect transparency are rare; the lighter shades being the more common. In
The brown and the green varieties are fairly common in the country. As indicated these are always tinged with yellow. The colours are due mainly to ferrous oxide while lithium and manganese could be contributory.
Tourmaline Brown
Chatoyant tourmalines are by no means uncommon and those displaying beautiful cat's eye effects are met with. As has been mentioned earlier chatoyancy in gem minerals is a reflection effect caused by acicular mineral inclusions or microscopic hollows or tubes which are assembled in a particular orientation to the crystal structure of the host mineral. A study of chatoyancy in tourmaline made by Graziani et. al (1982) has revealed that the effect is caused by acicular mineral inclusions or microscopic tubes. They expressed the opinion that the needle like inclusions were none other than tourmaline in most cases, except for a few which contained epidote. This revelation has been made after micro chemical analyses.
Colour changing chromiferrous tourmaline from
Tourmaline of Sri Lankan origin in foreign collections: -
Source: Colour Encyclopedia of Gemstones: Joel Arem (1977)
(1) Tourmaline: Brown 41.6 carats: Smithsonian Institute,
ZIRCON
The term zircon is said to have been derived from the Arabic word' Zargun' . The word 'jargoon' is apparently a corruption of this word and is the common local term for zircon. Zircons are plentiful in Sri Lanka and form a bulk of our exports among the less expensive categories. Zircons of all varieties are found among the gem gravels of this country, all of which have had their origins in certain rocks of the Central Highland/Southwestern Complex. Accordingly zircons are widespread in this country. The main areas from which zircons are recovered are Elahera, Nilgala, Passara, Nuwara Eliya, Haputale, Horana, Aluthgama, Matara, Ambalantota, Avissawella, Ratnapura, Rakwana, Morawaka, situated within the Avissawella Eheliyagoda- Kuruwita complex, the Ratnapura- Pelmadulla- Balangoda- Kahawatta complex, and the Rakwana-Bulutota-Morawaka-Deniyaya complex.
In composition, zircon is a silicate of zirconium (ZrSiO4) being a compound of silicon and zirconium. Apart from this it also has small amounts of iron and also uranium and thorium which have replaced zirconium during formation. The mineral crystallizes in the tetragonal system and is usually prismatic in habit and has pyramidal terminations. In certain types of zircon the presence of uranium and thorium within the host crystal has over the years (which could be in terms of millions) caused severe radio-active damage to the crystal lattice by perennial bombardment of alpha particles discharged by the uranium and thorium. These have eventually resulted in a complete breakdown in the crystal lattice and thereby made some material almost non crystalline or amorphous. In gemmological terminology such a process is known as metamictisation. Depending on the extent of radio-active decay, three types of zircon are identified - high, intermediate and low zircons. Where there is a considerable breakdown of the lattice the stones are identified as low type. Anderson (1963) is of the opinion that the Sri Lankan metamict zircons have undergone internal breakdown of structure much more than those from other localities both because of their geological age, being of Precambrian origin and also because the Lankan material contains comparatively more radioactive elements such as uranium and thorium. Woodhead et. al (1991) have stated that "metamictization increases systematically with the uranium-thorium content." As such it will be seen that the time period for metamictization of zircon depends on factors like the uranium thorium content within the stone. Consequently these three types have different properties showing differences in their densities, optical properties and their respective hardness. Accordingly it is said that the refractive indices of the high types (normal) are 1.928 and 1.945 and have a birefringence of 0.059 with a specific gravity of 4.69. These have a hardness of 7.5 in Mohs's scale. The colours in which this variety normally occurs are blue, golden-yellow, yellow and brownish-yellow. The low types are referred to as metamict zircons and because of their crystal lattice breakdown these are very nearly amorphous. These show refractive indices between 1.78 and 1.815 and their density could vary between 4.0 and 4.5. The properties of intermediate varieties as well as those of high and low types could vary depending on the extent of alpha-particle damage to the crystal structure.
Zircons as a group of gem minerals occur in a very wide range of colours. Among the many colours are yellow, deep orange, brownish-yellow, golden-yellow, reddishyefIow, pale straw-yellow, deep orange, brownish-orange, orange, brown, sky blue, green and deep red. Of these the deep orange, bright green, blue, and deep red are less common. Zircons of these colours when properly fashioned show an intense 'fire' and lustre thereby making such stones very attractive as gemstones. It has been often said of such stones that these could even rival the splendour and brilliance of diamonds. Colourless zircons are rare, although this state could be achieved through a process of heat. Most of the sky blue and colourless varieties in the markets today have undergone heat treatment. Pale straw-yellow colours could also be achieved by heating the inferior reddish and brownish-yellow varieties which are more common in nature and as abundant in Sri Lanka. Generally many colour varieties of zircon are remarkably susceptible to heat in a favourable manner which factor could consequently help in creating desirable shades of colour. Some varieties are even very sensitive to sunlight and if exposed to its direct rays for prolonged periods of time will result in losing their original colour and lustre. In some the colour becomes pale while in others it changes to brownish-red and finally brown. Therefore it is advisable not to expose one's jewellery set with zircons to the rays of the sun too often. Nevertheless it has been found that some revert to their original colours but with less brilliance, if stored in a dark environment for a reasonable period of time.
A common observation in most zircons is that these tend to show a cloudy appearance when viewed from certain directions, and display a strong double refraction which is very conspicuously seen in the doubling effect of the back facet edges (in facetted stones) when observed with the help of simple magnification (x 10 loupe). These are very helpful "on-the spot" diagnostic features. Because of the presence of radio-active elements zircon has a very characteristic absorption spectrum displaying a series of absorption lines throughout the spectrum.
The occurrence of colourless zircons in the Matara district has been noted as early as the early nineteenth century. However, it remains a factual coincidence that this district today is a major source for natural reddish brown zircons which could through a process of heat be de-colourised to a colourless state although one does not hear of natural colour less zircons from this region any more.
As mentioned earlier the low types of zircons are the product of crystal destruction by natural irradiation caused by inclusions of uranium and thorium. However it is known that low zircons could be restored to high types through a process of heat. Nassau (1980) mentions that if such stones are heated to temperatures of about 14000 C it usually repairs the crystal damage and become high zircons once more. Further, by heating natural brown to reddish brown zircons to temperatures of 10000 C one could achieve blue, colourless or yellow colours depending on the burning environment - either reducing or oxidizing conditions. The colourless and the sky blue could be achieved by heating under reducing conditions while the yellow and golden yellow is achieved under oxidizing conditions. It will be seen that sometimes the colourless state could be achieved under both reducing and oxidizing conditions. Heat treated blue zircons could revert to their original colours if exposed to ultra-violet light. As such these should not be exposed to excessive sunlight. By a further diversion of the technique of heat treatment chatoyancy could be produced in certain zircons. Through this technique fascinating results have been obtained in producing beautiful chatoyant zircons (cat's eye zircons) (Figure 15.1 0). Heat treated chatoyant zircons are now fairly abundant in the Sri Lankan market. Zircon cat's eyes have been reported as early as 1962 by Liddicoat and Gunawardene. According to Gunawardene (1988) chatoyant zircon in Sri Lanka is available in the untreated state as well, and such occurrences have been reported by Eppler (1958). The chatoyant effect could occur naturally or could be produced by heat treatment. Further their observations have revealed that the cat's eye effect in untreated stones was rather weak compared with the remarkable chatoyancy of their treated counterparts.
Refractive indices have indicated that the untreated types were intermediate zircons while the treated types were high zircons. This is probably because of the heat treatment, in which process zircon reverts to their high grades. The heat treated chatoyant zircons display much greater effect in comparison to their untreated counterparts and today heat treated ones are more abundant in Sri Lanka. It must be mentioned that excellent results have been achieved through this process of heat treatment in producing very beautiful zircon cat's eyes.
Sri Lankan Zircons in foreign collections:
Source: Colour Encyclopedia of Gemstones: Joel Arem (1977)
Gems in the Smithsonian Institute: Paul Desautels (1965)
(1) Brown Zircon: 118.1 carats: Smithsonian Institute, Washington D.C.
(2) Yellow Brown Zircon: 97.6 carats: Smithsonian Institute, Washington
D.C.
Beryl
Chemically, beryl is essentially a silicate of aluminium and beryllium. Being of an isomorphous group, beryllium could be replaced in small amounts by elements such as caesium, potassium, sodium and lithium while chromic oxide and ferrous oxide could replace aluminium. This phenomenon takes effect in causing slight changes in the optical and physical constants, like density and refractive indices in the different varieties of beryl. Beryl Crystallizesin the hexagonal system and all varieties are of uniform hardness being 7.5 in Mohs’s scale. If absolutely pure in composition beryl, should be colourless, but a vary close serutiny of such colourless material will reveal that these are more often that not vary faintly tinged with blue, green, pink, or yellow. Beryl occurs in different colours, such as grass green, blue green, yellowish green, yellow, pink and rose red. The different colours are attributed to the presence of different colouring elements like chromium, iron, lithium, etc. in the composition. Accordingly different varieties are identified. These are emerald, aquamarine, golden beryl (heliodor), morganite, and goshenite. Goshenite is the term applied to the colourless varieties.
Emerald is the most important member of this family, but this variety is not indigenous to
Morganite is a rose red or pink coloured variety of beryl which owes its colour to lithium. This variety too is not found among our gem gravels Morganite has a density of 2.80 and its refractive indices vary between 1.578 and 1.600 for the extraordinary ray and between 1.572 and 1.592 for the ordinary ray and the double refraction also varies accordingly between 0.008 and 0.010.
Aquamarine
The term aquamarine is applied to the pale blue, greenish blue and yellowish blue coloured beryl. The colours are mostly pale or light, the dark shades being less abundant. Aquamarine of a flawless deep blue or greenish blue colour is undoubtedly a stone of beauty. The colours of aquamarine are attributed to the presence of ferric oxide. The different shades of colour could be due to varying percentages of colouring oxides or as sometimes suggested it could be due to varying degrees of oxidation the colouring oxide have undergone. The depth of colour is most intense in large stones. The colour in smaller stones is comparatively lighter. Generally the colours in aquamarine are very well distributed and large flawless stones are by no means rare. Small liquid and solid inclusions found in some could cause turbidity while some could be perfectly transparent. In certain instances where inclusions are properly oriented in relation to the structure of the crystal, chatoyancy or asterism could be produced as the case may be. Stones of good quality should be of deep colour and perfect transparency.
Asteriated beryl has been found in
Aquamarine has a density variable between 2.69 and 2.71 and the refractive indices lie between 1.570 – 1.575 with birefringence of 0.005. The general colour of aquamarine has been often compared to the colour of sea water giving rice to the term aquamarine.
Most aquamarine are susceptible to heat treatment in the sense that this process could enhance the prevailing colours. This fact is made use of to maximum advantage in the industry through this practice of heat treatment of aquamarine is not resorted to in this country. Certain aquamarines from certain countries however do not react favourably to heat. In comparison the Brazilian stones are very favorably susceptible to this treatment resulting in beautiful blue green material which are plentiful in the market today.
In
Golden Beryl
This is a pure yellow variety of beryl and identified as heliodor. Here the colouring element is iron. Another yellow coloured beryl which apparently does not have the same richness, depth or colour nor lusture as that of golden beryl is also known.
Sri Lankan Beryl in Foreign Collections
Pale Green Beryl
Source: Gems in the Simthsonian Institute: Paul Desautels (1965)
(1) Aquamarine pale blue: 71.2 carats: Simthsonian Institute :
AMETHYST
History and romance. In the past, amethyst from
There is no shortage of localities for amethyst: Name almost any country and you'll find some deposit of the purple quartz. However, the most important source is
Colors. Most amethyst is a straight hue of purple, with varying degrees of tone and saturation. Everything from very light (almost colorless, as you might see on home shopping networks) to very dark, and from weak to vivid in saturations, is readily available. When tone and saturation are low, the gems tend to look somewhat pinkish. As mentioned above, the Russian material is best known for its reddish highlights. Siberian-quality color can be found in many locations but not in large amounts. Some material, as noted in gems from
Qualities. As expected with most transparent quartz, clarity can be literally flawless, especially in smaller stones of a few carats or less. In larger goods, 10 carats and up, expect to see some unimportant but possibly eye-visible inclusions, which may be a good thing (see "Synthetics" below). While the prominent color zoning from certain localities may decrease quality, it also can increase value because of its origin identification. The beauty of Four Peaks amethyst is two-fold: good color with positive identification features.
Enhancements and synthetics. Most amethyst is unenhanced, although some darker material is heated to lighten its color. In contrast, almost all citrine, the yellow-orange quartz, is heated amethyst. Only the commercially available citrine and ametrine from
While Russia may no longer be the source for the best natural-color amethyst, it is the best source for the finest quality synthetic amethyst. So much synthetic amethyst is in the market today that close to 50% of all amethyst in retail jewelry stores might be synthetic-and the store owners probably don't even know it. Since much of the synthetic material is free from identifiable inclusions, identification is a task for major gem laboratories with sophisticated equipment... and in most cases, the cost of identification is probably more expensive than the gem itself. Bulk testing in some laboratories has helped reduce the cost of amethyst identification.
Pricing. Because of the difficulty in identification, prices for small natural goods have merged with those for synthetics. Prices in The Guide for fine-quality I-ct. to 5-ct. stones range from $7 to $16 per carat. When there is positive natural identification, most likely in larger stones, prices can be elevated-to a point. Prices for fine-quality 10-ct. to 25-ct. amethyst range from $18 to $30 per carat. Over 25 cts., prices decrease, with prices for fine-quality goods ranging from $10 to $22 per carat.
Care and cleaning. Amethyst is durable and can be worn in all types of jewelry. However, as with all quartz (which has a hardness of 7), remember to wash off any dust before wiping the gem with a soft cloth. (Dust also has a hardness of 7 and can dull the surface of a polished gem.) Repolishing by a professional lapidary would be necessary to restore the luster of a dust-damaged gem.
Bench repair and setting. Amethyst is heat sensitive, so it is recommended that you remove or protect the stone from a jeweler's torch.
TOPAZ
Topaz occurs in the colours blue, blue green, brown, yellow, sherry yellow and pink. Red is extremely rare. It is said that pink as a natural occurrence. is also rare and that most of the pink stones available in the market today are invariably those that have been subjected to heat treatment. The dark yellow and the brownish stones from certain regions of the world when subject to slow heat could be transformed into pink. The colourless variety is the most abundant in
In the recent past the technique of inducing colour to colourless topaz by a process of irradiation developed rapidly. For this purpose different procedures have been adopted: - (i) gamma ray irradiation (ii) subjection to high energy electrons by the use of linear accelerators or (iii) with neutrons in neutrons in nuclear reactors (Schmetzer, 1987) Consequent to irradiation the clear colourless topaz takes on beautiful shades of blue. It has been found that topaz from Sri Lanka are the most susceptible to such treatment and produce the best results in respect of colours, as these have minimum impurities. What is more the Sri Lankan material has been found to 'cool off' in the least possible period of time after irradiation, thus reducing the radiation levels sufficiently for use as ornaments. These new irradiation possibilities generated a boom time bonanza for
Topaz is a fluo-silicate of aluminium combined with small amounts of ferrous oxide, lime, alkalies and water (hydroxyl). The water present is capable of replacing a certain amount of fluorine and this could cause slight variations in the optical and physical properties like the refractive indices and density, in stones of different localities. Accordingly the density could vary between 3.53 and 3.56. Its refractive indices could be 1.61-1.62 or 1.63-1.64, and its double refraction is 0.010. Topaz has a hardness of 8 in Mohs's scale. This mineral crystallizes in the orthorhombic system and has a marked cleavage in the direction of the basal plane. It has been noticed that minute fissures could develop on the cleavage planes and these minute fissures could produce brilliant iridescence which affect the transparency and clarity.
Of the colour varieties of topaz, yellow is said to be the most typical. Among the blue varieties, pure blue, greenish-blue and bluish varieties are known. The hues are invariably pale, making the occasional dark blue something very special. A very close observation of the stones will more often than not reveal a tinge of green. The pale colours could resemble aquamarine.
Impure colour, fissures in the cleavage planes, turbidity, cavities, both liquid and gaseous are common in practically all topaz.
White Topaz
MOONSTONE
(ORTHOCLASE FELDSPAR)
Moonstone is a member of the feldspar group of minerals. It is a grayish white and sometimes yellowish mineral displaying a fascinating shimmer. Feldspars are an important group of rock forming minerals and is of common occurrence. Of the many members of this group are the varieties orthoclase, microcline and plagioclase. Only orthoclase feldspar (moonstones) are of gem significance in relation to
Feldspar has a hardness of 6 in Mohs’s scale and its density varies between 2.56 and 2.7 in relation to the chemical composition of the different varieties. Feldspars are mostly dull in appearance and are translucent to opaque and are rarely transparent. The gem quality varieties have the property of displaying a beautiful shimmer as in moonstone or a play of colour as in labradorite. All varieties show two distinct sets of cleavage directions and are readily cleavable along these. The orthoclase variety crystallizes in the monoclinic system while the plagioclase and microcline varieties crystallize in the triclinic system. As a group feldspars could occur in the colours white, brown, red, green, and pale shades of yellow.
Moonstones are of the orthoclase group of the family of feldspars. Analysis has however revealed that its structure is in fact a combination of orthoclase and albite which is a sub variety of the plagioclase group. It is this combination that produces the shimmer and ‘blue seen ‘so favored in moonstones. Infact it actually contains albite in the orthoclase matrix. This creates an interference of light which in turn produces what is termed ‘Schillerisation’- the shimmer and the blue sheen effect.
Ideally, orthoclase and albite should be of a specific thickness, and arranged in alternating thin layers to produce the best effect. If the layers are too thick, the blue sheen effect will be lost, producing only a silky shimmer. The 'silky' sheen has been compared to the light of the moon. Hence its name moonstone. Moonstones are usually translucent although in its purest form it should be transparent and colourless. The characteristic shimmer and the blue sheen are most apparent in the orthoclase variety. The blue sheen in combination with a transparent and colourless body are rare and these make very attractive gemstones and are highly prized. In mineralogical terminology this effect is referred to as 'adularescence' and the material itself has been sometimes identified as adularia. As a common term all feldspars that display this sort of shimmer are collectively termed as adularescent feldspars. This characteristic interference of light is best observed in relation to a source of light. This effect seems to emanate from certain regions of the stone, giving the probable indication that this phenomenon is localized and not equally effective throughout. In better quality stones where the interference of light is optimum it displays a bluish tinted sheen. In order to produce the maximum effect moonstones should be cut 'en cabochon' although these are sometimes cut as flat pieces or rounded into beads of free sizes in order to get the maximum yield, in relation to the rough available.
Certain moonstones also show chatoyancy though not as effectively as other varieties that are capable of showing marked colour contrasts between the chatoyant streak and the body colour of the stone. However the skill of the lapidary could heighten this effect. The colour of moonstone is such that the line of demarcation between the eat's eye effect (streak) and the background colour of the stone does not show much contrast. Beautiful chatoyant moonstones are almost exclusively from
Sri Lankan moonstones have recorded densities between 2.56 and 2.58 the refractive indices being 1.525 and 1.520 having a double refraction of 0.005. The hardness is 6 in Mohs's scale. Orthoclase is essentially a potash feldspar (potassium aluminium silicate) conforming to the formula KAI Si3O8 Lankan material very often has stress cracks in the form of ladder like structures. These are often distinguishing features. The occurrence of amazonite (microcline feldspar) as mentioned earlier is more a rarity. A few samples have been picked up from time to time in and around Passara Lunugala regions. As observed, these are of a greenish blue colour, more inclined to turquoise blue with brownish streaks giving the appearance of a stain caused probably by oxidation of inclusions. This is by no means an attractive gemstone but could be polished as beads, should these be plentifully available. Amazonite is generally opaque and is of the same composition chemically as that of orthoclase being a potassium aluminium silicate. It has a slightly higher hardness than moonstone being 6.5 in Mohs's scale. The density varies between 2.56 and 2.58 and the refractive indices are 1.522 and 1.530 having a double refraction of 0.008.
Sri Lankan Moonstones in foreign collections
Source: Gems in the Smithsonian Institution: Paul E. Desautels (1965)
(1) Orthoclase Cat's eye: pale green 104.5 carats: Smithsonian Institute,
(2) Orthoclase Star: white 22.7 carats: Smithsonian Institute,
(3) Orthoclase Grey (cat's eye): 26 carats: Smithsonian Institute,
World’s Largest Rough Sapphire on Record
Weight - 40.30Kilo grams (201,500 carats)
Dimensions - Length 47cm, Breadth 29cm, Depth 28 cm
Owner - Mr.Jinadasa Guruge
Vidyala Mawatha,
Kahawatta,
Sri Lanka.
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