Rock Identifier
Sunstone (Feldspar variety) (Plagioclase Feldspar (Na,Ca)(Al,Si)4O8) — mineral
mineral

Sunstone (Feldspar variety)

Plagioclase Feldspar (Na,Ca)(Al,Si)4O8

Hardness: 6-6.5; Color: Reddish-brown, orange, or golden with metallic inclusions; Luster: Vitreous; Crystal Structure: Triclinic; Cleavage: Perfect in two directions; Specific Gravity: 2.62-2.72.

Hardness
6-6
Color
Reddish-brown, orange, or golden with metallic inclusions
Luster
Vitreous
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Physical properties

Hardness: 6-6.5; Color: Reddish-brown, orange, or golden with metallic inclusions; Luster: Vitreous; Crystal Structure: Triclinic; Cleavage: Perfect in two directions; Specific Gravity: 2.62-2.72.

Formation & geological history

Formed in igneous environments, typically within basaltic lava flows or pegmatites. The metallic 'schiller' effect or aventurescence is caused by tiny plate-like inclusions of copper or hematite deposited as the magma cools.

Uses & applications

Used primarily as a gemstone for jewelry (cabochons, beads, and faceted stones) and for metaphysical/collecting purposes.

Geological facts

The Oregon Sunstone is a famous variety that contains inclusions of pure copper. In Viking lore, similar stones (though often believed to be Iolite) were thought to be used as 'sunstones' for navigation on cloudy days.

Field identification & locations

Identify in the field by looking for 'aventurescence'—a glittering metallic flash visible just below the surface when tilted in the light. Often found in volcanic regions of Oregon (USA), Norway, and India.

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