How to identify Bronzite

To correctly identify Bronzite (Enstatite variety), 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

   Brownish-green to dark brown, often with golden or bronze reflections.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Submetallic to bronzy, vitreous on fresh fracture surfaces. The characteristic bronzy schiller is a key identifier.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, granular, or lamellar. Can be found as disseminated grains or larger crystals within host rocks.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Orthorhombic system. Crystals are usually prismatic, often with a square or rectangular cross-section. Cleavage is well-developed.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Two distinct cleavages at nearly 90 degrees (orthorhombic pyroxene cleavage), specifically {210} and {100} or {010} at 87° and 93°.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Mafic and ultramafic igneous rocks (e.g., norites, gabbros, peridotites, pyroxenites), high-grade metamorphic rocks, and occasionally in meteorites.

Key Facts

Hardness

5.5 - 6 on the Mohs scale.

Specific Gravity

3.2 - 3.3 (varies with Fe content).

Crystal System

Orthorhombic.

Color

Brownish-green to dark brown, often with a bronzy schiller.

Luster

Submetallic to bronzy, vitreous.

Transparency

Translucent to opaque.

Fracture

Uneven to conchoidal.

Cleavage

Perfect {210} and good {100} or {010} at nearly 90 degrees (87° and 93°).

Composition

Magnesium iron silicate, (Mg,Fe)SiO3, with Fe/(Mg+Fe) ratio typically between 0.1 and 0.3.

Physical characteristics

• Crystal Habit: Prismatic, often with a square or rectangular cross-section; also massive, granular, lamellar.
• Cleavage Type: Perfect {210} and good {100} or {010} at nearly 90 degrees (orthorhombic pyroxene cleavage).
• Fracture Type: Uneven to conchoidal.
• Tenacity: Brittle.
• Luster Type: Submetallic to bronzy (schiller), vitreous.

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