Spinel MgAl_{2}O_{4} Chrysoberyl BeAl_{2}O_{4} (_d_) SILICATES— Phenakite Be_{2}SiO_{4} Dioptase H_{2}CuSiO_{4} Peridot Mg_{2}SiO_{4} Zircon ZrSiO_{4} Enstatite MgSiO_{3} Diopside CaMg(SiO_{3})_{2} Nephrite CaMg_{3}(SiO_{3})_{4} Sphene CaTiSiO_{5} Benitoite BaTiSi_{3}O_{9} Andalusite Al(AlO)SiO_{4} Kyanite (AlO)_{2}SiO_{3} Topaz [Al(F,OH)]_{2}SiO_{4} Epidote Ca_{2}(Al,Fe)_{2}(AlOH)(SiO_{4})_{3} Euclase Be(AlOH)SiO_{4} Prehnite H_{2}Ca_{2}Al_{2}(SiO_{4})_{3} Iolite H_{2}(Mg,Fe)_{4}Al_{8}Si_{10}O_{37} { Hessonite Ca_{3}Al_{2}(SiO_{4})_{3} _Garnet_ { Pyrope Mg_{3}Al_{2}(SiO_{4})_{3} { Almandine Fe_{3}Al_{2}(SiO_{4})_{3} { Andradite Ca_{3}Fe_{2}(SiO_{4})_{3} Beryl Be_{3}Al_{2}(SiO_{3})_{6} Spodumene LiAl(SiO_{3})_{2} Jadeite NaAl(SiO_{3})_{2} Moonstone KAlSi_{3}O_{8} Tourmaline{12SiO_{2}.3B_{2}O_{3}.(9-x)[(Al,Fe)_{2}O_{3}].3x[ {(Fe,Mn,Ca,Mg,K_{2},Na_{2},Li_{2},H_{2})O].3H_{2}O Axinite HCa_{3}Al_{2}B(SiO_{4})_{4} Idocrase (Ca,Mn,Mg,Fe)_{2}(Al,Fe)(OH,F)]Si_{2}O_{7} (_e_) PHOSPHATES— Beryllonite NaBePO_{4} Apatite Ca_{5}(F,Cl)(PO_{4})_{3} Turquoise CuOH.6[Al(OH)_{2}].H_{5}.(PO_{4})_{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.