Petalite, also known as castorite, is a lithium aluminum phyllosilicate[7] mineral LiAlSi4O10, crystallizing in the monoclinic system.

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.

[citation needed] Petalite was discovered in 1800, by Brazilian naturalist and statesman Jose Bonifacio de Andrada e Silva.

[5][9][10] Economic deposits of petalite are found near Kalgoorlie, Western Australia; Aracuai, Minas Gerais, Brazil; Karibib, Namibia; Manitoba, Canada; and Bikita, Zimbabwe.

The first important economic application for petalite was as a raw material for the glass-ceramic cooking ware CorningWare.