How to identify Hypersthene

To correctly identify Hypersthene (Magnesium iron silicate), 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

   Dark brown, greenish-black, grayish-black. Often exhibits a bronze-like sheen or schiller.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to pearly on cleavage surfaces, submetallic to metallic on fractured surfaces, especially with schiller.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Typically massive, granular, or in lamellar aggregates. Can be prismatic.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Orthorhombic system, typically forming short, stout prismatic crystals, often with a rectangular cross-section. Can also be massive or lamellar.

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 degrees.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

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

Key Facts

Hardness

5 - 6 on Mohs scale

Specific Gravity

3.4 - 3.9 (increases with Fe content)

Crystal System

Orthorhombic

Color

Dark brown, greenish-black, grayish-black; often with bronze-like schiller

Luster

Vitreous to pearly on cleavage surfaces; submetallic to metallic on fractured surfaces (especially with schiller)

Transparency

Translucent to opaque

Fracture

Uneven to conchoidal

Cleavage

Perfect on {210}, good on {100} or {010} (nearly at 90 degrees)

Composition

(Mg,Fe)SiO3, where Fe/(Mg+Fe) is between 0.3 and 0.5

Physical characteristics

• Crystal Habit: Prismatic, massive, lamellar, granular
• Cleavage Type: Perfect prismatic (two directions at ~87° and ~93°)
• Fracture Type: Uneven to conchoidal
• Tenacity: Brittle
• Luster Type: Vitreous, pearly, submetallic, metallic

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