What is "petalite"

Petalite \Pet"al*ite\, n. [Cf. F. p['e]talite.] (Min.) A rare mineral, occurring crystallized and in cleavable masses, usually white, or nearly so, in color. It is a silicate of aluminia and lithia.

n. (context mineralogy English) A rare pegmatitic mineral, a lithium aluminosilicate, with the chemical formula lithiumaluminumsilicon₄oxygen₁₀; used in the manufacture of crystallized glass ceramics.

Petalite, also known as castorite, is a lithium aluminium phyllosilicate mineral Li Al Si O, crystallizing in the monoclinic system. Petalite is a member of the feldspathoid group. It occurs as colorless, grey, yellow, yellow grey, to white tabular crystals and columnar masses. Occurs in lithium-bearing pegmatites with spodumene, lepidolite, and tourmaline. Petalite is an important ore of lithium, and is converted to spodumene and quartz by heating to ~500 °C and under 3 kbar of pressure in the presence of a dense hydrous alkali borosilicate fluid with a minor carbonate component. The colorless varieties are often used as gemstones.