Bornite

Cu₅FeS₄

This specimen of bornite displays its characteristic iridescent tarnish, showing purplish and bronzy-gray hues, with brassy yellow chalcopyrite also present.

Bornite Physical Properties

Mohs Hardness

Crystal System

orthorhombic

Luster

metallic

Streak Color

grayish black

Cleavage

poor/indistinct on {111}

Fracture

conchoidal to uneven

Specific Gravity

4.9

Colors

copper-red, bronze-brown, purple, blue, red, black

Transparency

opaque

Type Locality

Montana, USA

Mineral Group

Sulfides

Uses

copper ore, collector

Associated Minerals

chalcopyrite, pyrite, chalcocite

Rarity

common

Geological Context

Bornite is a significant copper ore mineral found in various geological settings, including hydrothermal veins, porphyry copper deposits, and contact metamorphic deposits, often forming under high temperatures.

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