Montmorillionite

Formula:  (Na,Ca)_0.3(Al,Mg)₂Si₄O₁₀(OH)₂ ^. nH₂O

Origin of name:  After locality; Montmorillon, Vienne, France

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning: 

Unit cell: 

Colour:  White, gray, yellowish, greenish, pink

Diaphaneity: 

Luster:  Dull

Habit:  Massive, fine-grained; clay-like

Hardness:  1 to 2

Specific gravity:  2 to 3

Cleavage:  1; {001} perfect

Tenacity: 

Streak: 

Synonyms/varieties:

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