Durangite

Formula:   NaAl(AsO4)F

Origin of name:   Locality; State of Durango, Mexico

 

Crystal system:   Monoclinic

Crystal class:   2/m

Twinning:   Common in artificial crystals on {001}, penetration

Unit cell: a = 6.69 Å, b = 8.66 Å, c = 7.27 Å, b = 115.8°

 

Colour:  Pale yellow, light to dark orange to orange-red, red

Diaphaneity: Translucent

Luster:   Vitreous

Habit:   Crystals oblique pyramidal or prismatic elongated

Hardness:   5.5

Specific gravity:   3.90

Cleavage:   1; {110} distinct

Tenacity:   Uneven; brittle

Streak:   Yellowish

 

Synonyms/varieties:

 

Comments:

 

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