Polyhalite

Formula: K2Ca2Mg(SO4)4.2H2O

Origin of name: from Greek for many and salt

 

Crystal system: triclinic

Crystal class: unknown

Twinning: 

Unit cell: 

 

Colour: colourless, white, gray, pink to red from iron inclusions

Diaphaneity: transparent to translucent

Luster: vitreous to resinous

Habit: crystals highly modified tabular or elongated, twinned, rare, massive, fibrous to foliated

Hardness: 3.5

Specific gravit2.78y

Cleavage: 1; {10-1} perfect

Tenacity: 

Streak: 

 

Synonyms/varieties:

 

Comments: 

 

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