mineral

Sunstone (Heliolite)

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

Hardness: 6-6.5 (Mohs scale); Color: Yellow, orange, or reddish-brown with metallic flashes; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in two directions; Specific gravity: 2.62-2.72.

Hardness: 6-6
Color: Yellow, orange, or reddish-brown with metallic flashes
Luster: Vitreous to pearly

Identified March 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous environments, typically crystalline in lava flows (basalt) or within pegmatites. The metallic 'schiller' effect is caused by tiny inclusions of copper or hematite plates. Many famous deposits are dating from the Cenozoic era.

Uses & applications

Primarily used as a gemstone in jewelry (cabochons and faceted stones) and as a collector's specimen. In industry, feldspars are used in glass and ceramic manufacturing.

Geological facts

Sunstone was designated as the state gemstone of Oregon in 1987. Ancient Viking sagas mention 'sunstones' used for navigation, though historians debate if this refers to this mineral or calcite.

Field identification & locations

Identify in the field by its characteristic 'aventurescence' (metallic glitter) when rotated in light. Significant deposits are found in Oregon (USA), Norway, India, and Tanzania. Its hardness and cleavage help distinguish it from softer orange calcite.

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