TABLES
TABLE I
Chemical Composition of Gem-Stones
| (a) Elements— | ||
| Diamond | C | |
| (b) Oxides— | ||
| Corundum | Al2O3 | |
| Quartz | SiO2 | |
| Chalcedony | SiO2 | |
| Opal | SiO2.nH2O | |
| (c) Aluminates— | ||
| Spinel | MgAl2O4 | |
| Chrysoberyl | BeAl2O4 | |
| (d) Silicates— | ||
| Phenakite | Be2SiO4 | |
| Dioptase | H2CuSiO4 | |
| Peridot | Mg2SiO4 | |
| Zircon | ZrSiO4 | |
| Enstatite | MgSiO3 | |
| Diopside | CaMg(SiO3)2 | |
| Nephrite | CaMg3(SiO3)4 | |
| Sphene | CaTiSiO5 | |
| Benitoite | BaTiSi3O9 | |
| Andalusite | Al(AlO)SiO4 | |
| Kyanite | (AlO)2SiO3 | |
| Topaz | [Al(F,OH)]2SiO4 | |
| Epidote | Ca2(Al,Fe)2(AlOH)(SiO4)3 | |
| Euclase | Be(AlOH)SiO4 | |
| Prehnite | H2Ca2Al2(SiO4)3 | |
| Iolite | H2(Mg,Fe)4Al8Si10O37 | |
Garnet { | Hessonite | Ca3Al2(SiO4)3 |
| Pyrope | Mg3Al2(SiO4)3 | |
| Almandine | Fe3Al2(SiO4)3 | |
| Andradite | Ca3Fe2(SiO4)3 | |
| Beryl | Be3Al2(SiO3)6 | |
| Spodumene | LiAl(SiO3)2 | |
| Jadeite | NaAl(SiO3)2 | |
| Moonstone | KAlSi3O8 | |
| Tourmaline | 12SiO2.3B2O3.(9-x)[(Al,Fe)2O3].3x[(Fe, | |
| Axinite | HCa3Al2B(SiO4)4 | |
| Idocrase | (Ca,Mn,Mg,Fe)2(Al,Fe)(OH,F)]Si2O7 | |
| (e) Phosphates— | ||
| Beryllonite | NaBePO4 | |
| Apatite | Ca5(F,Cl)(PO4)3 | |
| Turquoise | CuOH.6[Al(OH)2].H5.(PO4)4 | |
TABLE II
Colour of Gem-Stones
Colourless and White.—Diamond, corundum (white sapphire), topaz, quartz (rock-crystal), zircon (when ‘fired’), moonstone; rarely beryl, tourmaline; among the less common species, phenakite, spodumene (colourless kunzite), beryllonite.
Yellow.—Diamond, topaz, corundum (yellow sapphire), quartz (citrine, Scotch or occidental topaz), tourmaline, zircon, sphene, spodumene, beryl.
Pink and Lilac.—Corundum (pink sapphire), spinel (balas-ruby), tourmaline (rubellite), topaz (usually when ‘fired’), spodumene (kunzite), beryl (morganite), quartz (rose-quartz).