How to identify Sunstone

To correctly identify Sunstone (Oligoclase (variety of Feldspar)), 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

   Typically orange, pink, red, yellow, or colorless, often with a metallic glitter. Can also be green.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to sub-vitreous, with a distinct metallic or spangled aventurescence.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth to slightly granular, depending on crystal size and habit.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Usually found as anhedral to subhedral grains in igneous rocks, or as well-formed tabular crystals in pegmatites. Often massive.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Perfect in two directions, nearly at right angles (approximately 90 degrees).

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Commonly found in mafic igneous rocks (e.g., basalt, gabbro), pegmatites, and some metamorphic rocks. Also found in placer deposits due to its relative hardness and resistance to weathering.

Key Facts

Hardness

6 - 6.5 on the Mohs scale

Specific Gravity

2.62 - 2.67

Crystal System

Triclinic

Color

Colorless, yellow, orange, pink, red, green; often with metallic glitter (aventurescence).

Luster

Vitreous to sub-vitreous, with aventurescence.

Transparency

Transparent to translucent.

Fracture

Uneven to conchoidal.

Cleavage

Perfect in two directions ({001} and {010}) at nearly 90 degrees.

Composition

Sodium calcium aluminum silicate, (Na,Ca)(Al,Si)AlSi2O8, with inclusions of hematite, goethite, or copper.

Physical characteristics

• Crystal Habit: Typically anhedral to subhedral grains, massive, or as tabular crystals.
• Cleavage Type: Perfect in two directions, nearly at right angles.
• Fracture Type: Uneven to conchoidal.
• Tenacity: Brittle.
• Luster Type: Vitreous to sub-vitreous, with aventurescence.

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