Althausite

Formula:  Mg₂(PO₄)(OH,F,O)

Origin of name:  For Egon Althaus (1933- ), German professor, Karlsruhe University, Karlsruhe, Germany

Crystal system:  Orthorhombic

Crystal class:  2/m 2/m 2/m

Twinning:

Unit cell: a = 8.258 Å, b = 6.054 Å, c = 14.383 Å

Colour:  Light gray, reddish brown

Diaphaneity: Translucent

Luster:  Vitreous

Habit:  Cleavable masses

Hardness:  3.5-4

Specific gravity:  2.97

Cleavage:  2; {001}perfect; {101} distinct

Tenacity:

Streak: White

Synonyms/varieties:

Comments:  Dimorphous with holtedahlite; colour caused by magnetite inclusions (?). Found in serpentine-magnesite deposits.