Epistilbite

Formula:   CaAl₂Si₆O₁₆ ^. 5H₂O

Origin of name:   From Greek for near and from stilbite

Crystal system:   Monoclinic

Crystal class:  

Twinning:   Universal on {100}; on {110}, penetration, cruciform

Unit cell: a = 9.0 Ǻ, b = 17.7 Ǻ, c = 10.2 Ǻ, β = 124.5°

Colour:  Colourless, white, pinkish

Diaphaneity:  Transparent to translucent

Luster:   Vitreous

Habit:   Crystals prismatic, always twinned; radiating spherical aggregates; granular

Hardness:   4

Specific gravity:   2.22 to 2.28

Cleavage:   1; {010} perfect

Tenacity: 

Streak: 

Synonyms/varieties:   Oryzite

Comments:   Dimorphous with goosecreekite