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Zircon and Zirconium Minerals; ZrSiO4 are colorless, pale yellow, grayish, yellowish green, brownish yellow, reddish brown; powder, white or nearly so; luster, like diamond, or glassy; H = 7.5; G = 4.68 to 4.70; crystals, tetragonal; cleavage, imperfect; composition silicate of zirconia (ZrO2).—Found in igneous rocks of the acidic kind, for example, syenite, and especially in pegmatite dikes; also, sometimes in crystalline limestone, schists, and gneiss. On account of its weight and hardness, it survives the destruction of these rocks by weathering, and so is found with placer gold, etc. The fíner crystals are used as jewels under the names of hyacinth (red and yellow) and jargon. A preparation called zirkite is on the market as a refractory. Zircon is the main source of the metal zirconium. Concentrates containing 95% of zircon sell well.
Thorite
Thorite; ThSiO4, with some water.—
This is a mineral similar to zircon, but is usually opaque-black; powder, dark brown; there is a yellow variety called orangeite; composition, silicate of thoria (ThO2). Thoria is used for making incandescent mantles for gas lighting. Recent developments suggest that thorium may be used, in due course, as a fissionable material the same as uranium. It is used also as an alloy with magnesium. Minerals containing thoria sell for about $100. a ton on the basis of not less than 6% of ThO2.
Beryl
Beryl; Be3Al2Si6O8.—Color, emerald-green, pale green, blue, yellow, white, sometimes rose red; powder, white; H= 7.5 to 8; G = 2.63 to 2.8; crystals, hexagonal; cleavage, poor. The green crystals, when transparent and free from flaws, are valuable as gems, then called emerald. It is the chief source of the metal beryllium.
Aquamarine
Aquamarine is a blue-green variety. Found in pegmatite granite dikes, or in gneiss or mica schist in contact with these dikes. The crystals are sometimes very large. Beryllium nitrate, made from beryl and other minerals containing beryllium, is used in the manufacture of gas mantles. Beryllium silicate is used in spark plugs. Value/ton for ore containing 10% to 12% of BeO depends.
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