Avogadrite

Formula:  (K, Cs)BF₄

Origin of name:  For Amadeo Avogadro (1776-1856), Italian physicist, University of Turin, Turin, Italy

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:

Unit cell: a = 8.659 Å, b = 5.480 Å, c = 7.030 Å

Colour: Colourless, white, yellowish to reddish

Diaphaneity: Translucent

Luster: Vitreous

Habit:  Crystals minute tabular to platy; dense crusts

Hardness:

Specific gravity:  2.50 to 3.00 (calculated)

Cleavage:  None

Tenacity:

Streak: Colourless

Synonyms/varieties:

Comments: Cubic above 273°C. Formed as a sublimation product around volcanic fumaroles.