Holtedahlite

Formula:  Mg₁₂(PO₃OH,CO₃)(PO₄)₅(OH,O)₆

Origin of name:  For Olaf Holtedahl, Norwegian geologist

Crystal system:  Hexagonal

Crystal class:  3m

Twinning: 

Unit cell: 

Colour:  Colourless

Diaphaneity: 

Luster:  Vitreous

Habit:  Irregular patches

Hardness:  4.5 to 5

Specific gravity:  2.94

Cleavage:  None

Tenacity: 

Streak: 

Synonyms/varieties:

Comments:  Dimorphous with althausite