Petalite Locality: Mogok, Pyin Oo Lwin District, Mandalay Division, Burma (Myanmar) (Locality at mindat.org) Size: miniature, 3.8 x 2.4 x 1.6 cm Petalite A 17-g — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Petalite
Also known as: Castorite.
A lithium-aluminium sheet silicate of granite pegmatites — 'castorite' — an ore of lithium and a source of thermal-shock glass.
Intro adapted from Wikipedia (CC BY-SA).
Petalite is an IMA-recognized mineral species in the silicate class, with the chemical formula LiAlSi₄O₁₀.
It crystallizes in the monoclinic crystal system (space group P2/c).
Key properties: Mohs hardness 6–6.5; specific gravity 2.41–2.42; typically colorless or white or gray or pink; White streak; Vitreous, pearly on {001} luster; refractive index 1.51; optically biaxial.
IMA symbol Ptl, grandfathered status — known before the IMA’s founding, named in 1800.
Found in granite pegmatites, locally constituting an ore of lithium.
It is found associated with Spodumene, pollucite, lepidolite, tourmaline, topaz, albite, microcline, quartz.
Its name comes from the Greek for leaf, in allusion to its perfect basal cleavage.
Collections: Collector Favorites, Gemstones.