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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 crystalsoccur
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
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