Gemstones | Benitoite | Iolite | Fluorite etc | Bahadur: Handbook of Precious Stones Page 159



	and other areas. A good locality in India is in the Kishengarh State, Rajputana. 22. Spodumene.—It is a silicate of lithium and aluminium and forms greenish-grey crystals. Two varieties are used as gems: (i) Hiddenite—yellow-green to emerald green, and (ii) Kunzite—delicate pink to lilac in colour. Both are transparent. Monoclinic and it occurs in large crystals and tabular masses. Cleavage: prismatic and parting pinacoidal. Hardness = 6 to 7. Specific gravity = Colour: white, grey, green or purple. Lustre is vitreous to pearly. Transparent to opaque. Mean refractive index ==. Double refraction = Coloured varieties are pleochroic; kunzite is phosphorescent. The kunzite variety is obtained near Pala, California and Madagascar. The spotted and transparent variety comes from Brazil. 23. Staurolite.—Orthorhombic, and is a complex alumino-silicate of iron and magnesium. It forms cross-shaped twins and is often worn as charms, and is used by the clergy due to cross-shaped twins. Hardness = 7 to Specific gravity = Colour: reddish-brown. Translucent to opaque. Pleochroic. Mean refractive index = Good crystals come from St. Gothard, Switzerland, from the Tyrol, in Brazil and Virginia. 24. Sphene makes an attractive gem, but is rather soft. Colour: yellow, green or brown. Lustre: adamantine, transparent to opaque. Refractive index is very high,„ Composition: Good crystals occur in schists or limestone in Switzerland, Tyrol and many other localities; also in Madagascar, Maine, New York and Pennsylvania. 25. Idocrase (Vesuvianite).—It resembles jade, cyprine is a blue variety. Tetragonal. Hardness =. Specific gravity = Colour varies from yellow, green, brown, blue, red, etc. It is translucent with a glassy lustre, etc. Mean refractive index = It is found 160