Petalite

Petalite Mogok, Burma Miniature, 3.8 x 2.4 x 1.6 cm © irocks

Chemical Formula: LiAl(Si4O10)
Name Origin: From the Greek petalon – “leaf” in allusion to the perfect basal cleavage.
Petalite, also known as castorite, is a lithium aluminium phyllosilicate mineral LiAl(Si4O10), 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.

Discovery and occurrence

Discovered in 1800, type locality: Utö Island, Haninge, Stockholm, Sweden. The name is derived from the Greek word petalon, which means leaf.

Economic deposits of petalite ahre 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. It has been used as a raw material for ceramic glazes.

History

Discovery date : 1800
Town of Origin : ILE UTO
Country of Origin : SUEDE

Optical properties

Refractive Index: from 1,50 to 1,52
Axial angle 2V: 82-84°

Physical properties

Hardness: 6,50
Density : from 2,41 to 2,42
Color : colorless; white; grey; yellowish grey; yellow; reddish; greenish; pink
Luster: vitreous; nacreous
Streak : white
Break: sub-conchoidal
Cleavage : Yes

Photos:

Petalite (faceted) Pech, Kunar Province, Afghanistan Thumbnail, 1.6 x 1.6 x 1.1 cm © irocks
Petalite Locality: Palelni mine, Khetchel Village, Molo Quarter, Momeik Township, Shan Sate, Burma (Myanmar) Specimen Size: 2.3 x 1.5 x 1.1 cm (thumbnail) © minclassics
Petalite Locality: Palelni mine, Khetchel Village, Molo Quarter, Momeik Township, Shan Sate, Burma (Myanmar) Specimen Size: 2.4 x 2.3 x 1.8 cm (thumbnail) © minclassics
SHARE