Mirabilite

Formula:  Na₂SO₄ ^. 10H₂O

Origin of name:  From Latin sal mirabile - miracle salt

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning: 

Unit cell: 

Colour:  Colourless, white

Diaphaneity:  Transparent to opaque

Luster:  Vitreous

Habit:  Crystals long prismatic or acicular, or resemble borax; granular to fibrous aggregates; efflorescent crusts

Hardness:  1.5 to 2

Specific gravity:  1.464

Cleavage:  4; {100} perfect; {001}, {010} and {011} traces

Tenacity: 

Streak: 

Synonyms/varieties:

Comments: Dehydrates quickly in dry air and must be preserved in a closed box.