4.10. Feldspar Group of Gems

[Full title: Item-wise Discussion on Gems with Decreasing Hardness; (10): Feldspar Group of Gems]

RAIS 130 g represents the general group of feldspar minerals where R may be potassium (partly replaced by sodium) in orthoclase and microcline, or sodium (partly replaced by calcium) in plagio- -clase. Moonstone, available in Sri Lanka, is a microperthitic to sub-microperthitic intergrowth of orthoclase and albite in an arrangement of thin layers exhibiting a pearly opalescent reflection or shiller or a delicate play of colours. It has a beautiful blue bloom and lovely sheen. Sunstone is a variety of oligoclase, Na-Ca feldspar containing little K and Ba feldspar. A play of colour-fire-red, yellow, blue, green etc.)-is a common characteristic of sunstone; this is due to interference of light, caused by reflection from thin lamellar inclusions of various minerals such as hematite, goethite etc. Usually this mineral is associated with igneous rock. s t Nandaka and si tavrsti in AS. 2.11.31-32 could have been moonstone, which was mentioned as sasikanta in Brahatsamhita (BS. 80.4) and Rayanaparikkha (Rayanaparikkha 96), and as candrakanta in other texts such as Navaratnapariksa (Navaratnapariksa 154 & 156), Ratnasangraha (RS 18) and Manimala (Manimala 436 & 438). The typical description of candrakanta is: purvendukarasamsparsat amrtam sati lagat | ksati candrakanti tat akhyata m durlabham scat kalau yuge ||

VII-50 That which runs nectar when the moon at its full bathes it with its balmy influence, is called candrakanta' (Navaratnapariksa 156; Manimala 438). Sanskrit literature is replete with 'candrakanta slabs on which lovers in separation seek solace'. Could these be plain marble? The Ratnasastra texts (Navaratnapariksa 154 & 156, RS 18, Manimala 436 & 438, Rayanaparikkha 96) claim that candrakanta is a variety of sphatika or quartz. But we believe that candrakanta is moonstone, a variety of feldspar defined earlier, which was available in Sri Lanka only. As it stands admitted in Navaratnapariksa 156 (durlabham'), it was rarely available. in India. suryakanta or Ravikanta (AS. 2.11.32, Navaratnapariksa 154-155, RS 18, Manimala 436-437 and Rayanaparikkha 96) could however belong to the quartz family as claimed in the above-cited literatures. We have earlier quoted Navaratnapariksa 155: suryasu sparsamatrena valim vamati which means 'fire emerges when sun-rays pass though', and implies that survakanta could mean a lens of transparent rock crystal. Alternatively, it could be sunstone of the feldspar family as defined earlier. Hiuen Tsang (629 A.D.) mentioned about Yun-shih rock near the Tiladaka monastery in Magadha. It has been translated as cloud- - stone or 'variegated marble' (Samuel Beal: Buddhist records of the Western World, 1969, Book VIII, p. 103). It could be a siliceous rock as well.

VII-51 We may briefly comment on fine yellowd sh-green or golden yellow Chrysolite (French jewellers call it peridot), which is precious olivine or a gem variety of the group of mineral called olivine, R 2+ R 2+ (S 104) wherein R, and R₂ could be various combinations of Mg, Fe, Ca amd Mn. Chrysolite contains more of. 2+ Mg and Fe" accounting for the typical colour. Its hardness is 6%; it is slightly softer than quartz and its specific gravity is 3.33-3.37, more than that of emerald. At present, the reserves of the gem probably stand exhausted, but in the ancient world, it was well-known and created some confusion with emerald (green) and topaz (yellow), all the three gem minerals occurring together betweer the Nila and the Red Sea. E.S. Dana has commented that 'the chrysolithus of Pliny was probably our topaz and his topaz our chrysolite'. The two different materials could be easily distin- -guished in terms of their hardness, topaz being much harder. The above confusion between chrysolite and topaz was connected with the Sanskrit words: pita meaning yellow and pittaka meaning colour of bile what is green or greenish-yellow. Arthasastra mentioned a gem pittaka (AS 2.11.35) which was most possibly chrysolite.. Later, another name came up: 'rucaka which is yellow, green, red or tawny, found in the borders of Kashmir' (quoted by Tagore in Manimala pp. 508-509), and this also could be chrysolite. The Sanskrit word pita was converted to pittdoh in Hebrew and then to tipdoh and topazion. The confusion between pittaka chrysolite and pita topaz is now a matter of history.