Perhamite

Formula: Ca3Al7(SiO4)3(PO4)4(OH)3.16.5H2O

Origin of name: for F. Perham, American geologist

 

Crystal system: hexagonal

Crystal class: 6/m 2/m 2/m

Twinning: 

Unit cell: a = 7.022 Å, c = 20.18 Å

 

Colour: brown

Diaphaneity: 

Luster: dull, vitreous on cleavage

Habit: crystals platy, in spherulitic masses to 1 mm, rare

Hardness: 5

Specific gravity: 2.64

Cleavage: none

Tenacity: brittle

Streak: white

 

Synonyms/varieties:

 

Comments: 

 

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