Prosopite

Formula: CaAl2(F,OH)8

Origin of name: from Greek for mask

 

Crystal system: monoclinic

Crystal class: 2/m

Twinning: 

Unit cell: 

 

Colour: colourless, white, gray

Diaphaneity: transparent to translucent

Luster: vitreous

Habit: crystals tabular, minute, embedded blades or bundles, massive, fine granular to powdery

Hardness: 4.5

Specific gravity: 2.89

Cleavage: 1; {111} perfect

Tenacity: 

Streak: 

 

Synonyms/varieties:

 

Comments: 

 

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