Petalite

Lore & Background

Petalite, also called castorite, is a lithium aluminum phyllosilicate mineral with the formula LiAlSi4O10. It crystallizes in the monoclinic system and typically appears as colorless, pink, grey, yellow, yellow-grey, or white tabular crystals, as well as columnar masses. The mineral’s name comes from the Greek word petalon, meaning “leaf,” in reference to its perfect cleavage. Its type locality is Utö Island, Haninge, Stockholm, Sweden, and it was discovered in 1800 by Brazilian naturalist and statesman José Bonifácio de Andrada e Silva.

Petalite is found in lithium-bearing pegmatites, often alongside spodumene, lepidolite, and tourmaline. Significant economic deposits occur near Kalgoorlie, Western Australia; Aracuai, Minas Gerais, Brazil; Karibib, Namibia; Manitoba, Canada; and Bikita, Zimbabwe. The mineral is an important ore of lithium. When heated to approximately 500 °C under 3 kbar of pressure in the presence of a dense hydrous alkali borosilicate fluid with a minor carbonate component, petalite converts to spodumene and quartz.

This secondary spodumene, along with petalite itself, contains less iron than primary spodumene, making it a more desirable source of lithium for applications such as glass production. Colorless varieties are sometimes used as gemstones. Historically, petalite is significant because the element lithium was first identified from this mineral in Sweden in 1817; the element was named from the Greek word for “stone” due to its discovery in petalite. The first major economic use of petalite was as a raw material for the glass-ceramic cookware CorningWare, and it has also been employed in ceramic glazes.

Reader's Guide

The element was named 'lithium' from the Greek word for 'stone' due to its discovery in this mineral. Petalite and secondary spodumene formed from it are lower in iron than primary spodumene, making it a more useful source of lithium in applications such as glass production.

Colorless varieties are often used as gemstones. The first important economic application for petalite was as a raw material for the glass-ceramic cooking ware CorningWare, and it has also been used in ceramic glazes. Economic deposits are found near Kalgoorlie, Western Australia; Aracuai, Minas Gerais, Brazil; Karibib, Namibia; Manitoba, Canada; and Bikita, Zimbabwe.