Elpidite

Formula:   Na₂ZrSi₆O₁₅ ^. 3H₂O

Origin of name:   From Greek for hope

Crystal system:   Orthorhombic

Crystal class:   mm2

Twinning:   Noted

Unit cell: a = 7.14 Ǻ, b = 14.68 Ǻ, c = 14.65 Ǻ

Colour:  Colourless, yellowish white, tan, yellowish brown, light brick-red

Diaphaneity:

Luster:   Vitreous or silky

Habit:   Crystals thin prismatic, striated vertically; aggregates of fan-shaped fine fibres

Hardness:   5

Specific gravity:   2.52 to 2.

Cleavage:   2; Prismatic, two directions perfect

Tenacity: 

Streak: 

Synonyms/varieties:

Comments: