Gaudefroyite

Formula:  Ca4Mn3-x(BO3)3(CO3)(O,OH)3

Origin of name:  For C. Gaudefroy, French mineralogist

 

Crystal system:  Hexagonal

Crystal class:  6

Twinning:

Unit cell: a = 10.6 Ǻ, c = 5.90 Ǻ

 

Colour:  Black

Diaphaneity:

Luster:  Brilliant to dull

Habit:  Hexagonal prisms, acicular to stubby

Hardness:  6

Specific gravity:  3.35 to 3.50

Cleavage:  None

Tenacity:  Conchoidal; brittle

Streak: 

 

Synonyms/varieties:

 

Comments:

 

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