Mountainite

Formula:  (Ca,Na₂,K₂)₂Si₄O₁₀ ^. 3H₂O

Origin of name:  Named for Edgar Donald Mountain, Professor of Geology, Rhodes University, Grahamstown, South Africa.

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning: 

Unit cell: a = 13.51, b = 6.55, c = 13.51, β = 104°

Colour:  White

Diaphaneity: Transparent to translucent

Luster:  Silky

Habit:  Fibrous, matted, silky, in rosettes to 2.0 mm

Hardness:  3

Specific gravity:  2.36

Cleavage:  None

Tenacity: 

Streak: White

Synonyms/varieties:

Comments:  Related to delhayelite