18 Photos
Petalite
Chemical Formula	LiAlSi4O10
Species	Silicates
Crystal System	Monoclinic
Mohs Scale	6
Specific Gravity	2.4
Color	Colorless, grey, yellow, pink, to white
Streak	Colorless
Luster	Vitreous
Refractive Index	n = 1.504 n = 1.510 n = 1.516
Diaphaneity	Transparent, Translucent
Cleavage	PerfectPerfect on poor on
Fracture	Conchoidal
Crystal Habit：Tabular prismatic crystals and columnar masses
Geological Setting：Lithium-rich pegmatites.

Petalite, also known as castorite, is a lithium aluminium tectosilicate mineral LiAlSi₄O₁₀, crystallizing in the monoclinic system. Petalite is a member of the feldspathoid group. It occurs as colourless, 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.

Discovered in 1800, type locality: Ut? Island, Haninge, Stockholm, Sweden. The name is derived from Greek petalon for leaf.