Poudretteite

Poudretteite is an extremely rare mineral and gemstone that was first discovered as minute crystals in Mont St. Hilaire, Quebec, Canada, during the 1960s.^[6] The mineral was named for the Poudrette family because they operated a quarry in the Mont St. Hilaire area where poudretteite was originally found, and the quarry is currently owned by the United Kingdom based Salmon Mining Industries Inc. Poudretteite has a barely detectable radioactivity.^[7]

Poudretteite
General
Category	Cyclosilicate
Formula	KNa2B3Si12O30
IMA symbol	Pou[1]
Strunz classification	9.CM.05
Dana classification	63.02.01a.08
Crystal system	Hexagonal
Crystal class	Dihexagonal dipyramidal (6/mmm) H-M symbol: (6/m 2/m 2/m)
Space group	P6/mcc
Unit cell	1,221.72 ų
Identification
Color	Colorless, Light pink
Crystal habit	Roughly equant barrel-shaped prismatic crystals
Cleavage	None
Fracture	Conchoidal, splintery
Tenacity	Brittle
Mohs scale hardness	5
Luster	Vitreous (Glassy)
Streak	White
Diaphaneity	Transparent
Specific gravity	2.51
Density	2.51
Optical properties	Uniaxial (+)
Refractive index	1.511 to 1.532
Birefringence	0.021
Pleochroism	Colorless to pink
References	[2][3][4][5][6]