Natrophosphate

Formula: Na₇(PO₄)₂F.19H₂O

Origin of name: from composition

Crystal system: Cubic/isometric

Crystal class: 4/m 3 2/m

Twinning: 

Unit cell: a = 27.79

Colour: Colourless, white

Diaphaneity: Transparent

Luster: Vitreous to greasy

Habit: Massive, radial, fibrous

Hardness: about 2.5

Specific gravity: 1.71 to 1.72

Cleavage: 1; {111} imperfect

Tenacity: Conchoidal fracture

Streak: White

Synonyms/varieties:

Comments: surface alters to a secondary powdery coating on exposure to air, fluoresces weak orange in ultraviolet light