How to identify Bornite with Malachite

To correctly identify Bornite with Malachite (Cu5FeS4 with Cu2(CO3)(OH)2), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Bornite: Freshly broken surfaces are reddish-brown to copper-red, rapidly tarnishing to iridescent purples, blues, and reds (peacock colors). Malachite: Bright green to dark green, often banded.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Bornite: Metallic. Malachite: Silky, dull, or earthy in massive forms; vitreous to adamantine in crystalline forms.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Bornite: Typically massive, granular, or disseminated. Malachite: Often botryoidal, stalactitic, fibrous, or massive; sometimes as crusts or coatings.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Bornite: Isometric system, rarely forms distinct cubic, dodecahedral, or octahedral crystals; usually massive. Malachite: Monoclinic system, rarely forms distinct crystals; typically found in botryoidal, reniform, stalactitic, or massive habits, often with concentric banding.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Bornite: Poor, indistinct, or absent. Malachite: Perfect on {201}, good on {001}.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in the oxidized zones of copper sulfide deposits. Bornite is a primary ore mineral in hydrothermal veins, porphyry copper deposits, and contact metamorphic deposits. Malachite forms secondarily from the weathering of bornite and other copper sulfides in the presence of carbon dioxide and water.

Key Facts

Hardness

Bornite: 3.0-3.25 on Mohs scale. Malachite: 3.5-4.0 on Mohs scale.

Specific Gravity

Bornite: 4.9-5.3. Malachite: 3.9-4.03.

Crystal System

Bornite: Isometric. Malachite: Monoclinic.

Color

Bornite: Reddish-brown to copper-red, tarnishing to iridescent purples, blues, reds. Malachite: Bright green to dark green.

Luster

Bornite: Metallic. Malachite: Silky, dull, earthy, vitreous to adamantine.

Transparency

Bornite: Opaque. Malachite: Translucent to opaque.

Fracture

Bornite: Uneven to conchoidal. Malachite: Uneven to subconchoidal.

Cleavage

Bornite: Poor, indistinct, or absent. Malachite: Perfect on {201}, good on {001}.

Composition

Bornite: Copper iron sulfide (Cu5FeS4). Malachite: Copper carbonate hydroxide (Cu2(CO3)(OH)2).

Physical characteristics

• Crystal Habit: Bornite: Massive, granular, disseminated, rarely cubic, dodecahedral, or octahedral crystals. Malachite: Botryoidal, reniform, stalactitic, fibrous, massive, crusts, rarely acicular crystals.
• Cleavage Type: Bornite: Indistinct. Malachite: Perfect in one direction, good in another.
• Fracture Type: Bornite: Uneven to conchoidal. Malachite: Uneven to subconchoidal.
• Tenacity: Bornite: Brittle. Malachite: Brittle.
• Luster Type: Bornite: Metallic. Malachite: Silky, dull, earthy, vitreous to adamantine.

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