mineral

Sunstone

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

Hardness: 6-6.5 (Mohs scale); Color: Orange, reddish-brown; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in two directions; Schiller effect (aventurescence) from internal copper or hematite platelets.

Hardness: 6-6
Color: Orange, reddish-brown
Luster: Vitreous to pearly

Identified April 1, 2026More mineral →

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Physical properties

Formation & geological history

Forms in igneous rocks like basalt and latite flows. The distinct 'sunstone' flash is caused by microscopic inclusions of copper or hematite that orient flatly during volcanic cooling. Most gem-grade specimens are Cenozoic in age.

Uses & applications

Primarily used as a gemstone in rings, pendants, and earrings. High-quality specimens are prized by mineral collectors for their optical properties.

Geological facts

The Oregon Sunstone is the official state gemstone of Oregon, USA. It is one of the few gemstones that contains naturally occurring copper flakes, which produce a unique 'schiller' effect not seen in other feldspars.

Field identification & locations

Identify by the 'aventurescence'—a metallic-like glitter when rotated under light. Common locations include Oregon (USA), Norway, Tanzania, and India. Collectors should look for vibrant color and a high concentration of schiller inclusions.