How to identify Bronzite

To correctly identify Bronzite (Enstatite (variety Bronzite)), 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

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

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Submetallic to bronzy (schiller), vitreous on fresh fracture surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, granular, or columnar. The schiller is a key textural feature.

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, but well-formed crystals are rare in massive occurrences. More commonly found as anhedral to subhedral grains.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect cleavage in two directions at nearly 90 degrees (orthorhombic pyroxene cleavage).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

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

Key Facts

Hardness

5-6 on the Mohs scale

Specific Gravity

3.2-3.3 (varies with iron content)

Crystal System

Orthorhombic

Color

Greenish-brown, dark brown, often with a bronzy schiller.

Luster

Submetallic to bronzy, vitreous on fresh fracture.

Transparency

Opaque to translucent.

Fracture

Uneven to conchoidal.

Cleavage

Perfect on {210} and {100} at nearly 90 degrees.

Composition

Magnesium iron silicate, (Mg,Fe)SiO3, with Fe/(Mg+Fe) typically between 10-30 mol%.

Physical characteristics

• Crystal Habit: Prismatic, columnar, massive, granular. Often anhedral to subhedral grains in rock matrices.
• Cleavage Type: Perfect in two directions at approximately 90 degrees (orthorhombic pyroxene cleavage).
• Fracture Type: Uneven to conchoidal.
• Tenacity: Brittle.
• Luster Type: Submetallic to bronzy (schiller), vitreous.

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