Bournonite

PbCuSbS₃

This specimen displays dark, metallic, blocky crystals of Bournonite, likely exhibiting its characteristic 'cogwheel' twinning, with a pen for scale.

Bournonite Physical Properties

Mohs Hardness

2.5

Crystal System

orthorhombic

Luster

metallic

Streak Color

blackish-gray

Cleavage

distinct on {010}, less distinct on {001} and {110}

Fracture

conchoidal to uneven

Specific Gravity

5.8

Colors

steel-gray, iron-black, lead-gray

Transparency

opaque

Type Locality

Příbram (Czech Republic), Neudorf (Germany), Cornwall (England), Huaron (Peru)

Mineral Group

Sulfosalts

Uses

minor ore of lead, copper, and antimony, collector

Associated Minerals

galena, sphalerite, tetrahedrite, chalcopyrite, pyrite, quartz

Rarity

uncommon

Geological Context

Bournonite typically forms in hydrothermal veins at low to moderate temperatures, often found in lead-zinc-silver deposits associated with other sulfide minerals.

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