Photo of Petalite in Processed & Rough Form
Petalite is a mineral with a hardness of 6 out of 10 on the Mohs scale of mineral hardness [?]. These Monoclinicly structured gems are made of lithium aluminum silicate, their full chemical compound being Li2OAl2O38SiO2.
Petalite is a lithium aluminum silicate that is an important ore of lithium.
This mineral forms, rarely, as small crystals, which are commonly twinned. More often, petalite forms as large, cleavable masses. It may be white, grey, pinkish, yellow, or colorless. It is transparent to translucent, with a vitreous to pearly luster, and fuses with difficulty.
It forms in very coarse-grained, acid igneous rocks. It is associated with a number of minerals, including quartz, and lepidolite, spodumene, and other lithium-rich minerals.
Fine, transparent masses are common at Varutrask (Sweden), Bikita (Rhodesia), South Africa, Finland, and Australia. Fine, terminated crystals were found in Norwich, Massachusetts (USA). It is also found in granite on the island of Elba (Italy) and in Wyoming, California, Oxford County-Maine (USA), Russia, Brazil, Zimbabwe, and Namibia.
Varieties are called castor or castorite. There are some rare varieties of petalite cat's eyes.
Petalite is also called lithia-feldspar, and lithium-feldspar.
It is often confused with other colorless gems and glass.
The specific gravity [?] for Petalite is 2.42, its refractive index [?] is 1.50-1.51, and its double refraction [?] is 0.014.
History
Petalite derives its name from the Greek "petalon" meaning "leaf." It was discovered in 1800, in Sweden.
Industrial Usages
Petalite mineral was used to manufacture glass-ceramic cooking ware CorningWare. It has been used as a raw material for ceramic glazes.
Petalite crystal is cut as faceted gems and prized by collectors. Some stone shows chatoyancy such as petalite-analcime cat's-eye.
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