Bournonite

Formula:  PbCuSbS3

Origin of name:  For Count  Jacques Louis de Bournon, French crystallographer and mineralogist (1751-1825)

 

Crystal system:  Orthorhombic

Crystal class:  mm2

Twinning:  Very common on {110}, repeated, cruciform, or cogwheel aggregates

Unit cell: a = 8.168 Ǻ, b = 8.712 Ǻ, c = 7.811 Ǻ

 

Colour:  Steel-gray to iron-black

Diaphaneity: Opaque

Luster: Brilliant to dull

Habit:  Crystals short prismatic or tabular; massive, granular

Hardness:  2.5 to 3

Specific gravity:  5.83

Cleavage:  3; {010} imperfect, {100} and {001} less perfect

Tenacity:  Subconchoidal to uneven; brittle

Streak:  Steel-gray to iron-black

 

Synonyms/varieties:  Cog-wheel-ore, endellionite

 

Comments:  Series with seligmannite. Found in hydrothermal veins formed at moderate temperatures

 

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