mineral
Sunstone (Oligoclase / Plagioclase Feldspar)
(Na,Ca)(Al,Si)4O8 with Hematite or Goethite inclusions
AI-generated identification · may be incorrectHardness: 6 - 6.5 on Mohs scale; Color: Orange, reddish-brown, peach, with metallic flashes (aventurescence); Luster: Vitreous to sub-vitreous; Crystal system: Triclinic; Cleavage: Perfect in two directions intersecting at nearly 90 degrees; Specific gravity: 2.62 - 2.65.
- Hardness
- 6 - 6
- Luster
- Vitreous to sub-vitreous
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Physical properties
Hardness: 6 - 6.5 on Mohs scale; Color: Orange, reddish-brown, peach, with metallic flashes (aventurescence); Luster: Vitreous to sub-vitreous; Crystal system: Triclinic; Cleavage: Perfect in two directions intersecting at nearly 90 degrees; Specific gravity: 2.62 - 2.65.
Formation & geological history
Formed in igneous environments, typically crystallized from lava flows or within granitic pegmatites. The characteristic glitter is caused by microscopic oriented inclusions of hematite, copper, or goethite plates exsolved during cooling.
Uses & applications
Predominantly used as a gemstone for cabochons, beads, and carved ornamental jewelry, as well as being a popular tumbled stone for mineral collectors and metaphysical practices.
Geological facts
According to Norse lore, a 'sunstone' was reportedly used as a navigational instrument to locate the sun on overcast days through light polarization, although historical debate continues on whether it was feldspar sunstone or Iceland spar calcite.
Field identification & locations
Identified by its distinctive shimmering Schiller effect (aventurescence) and feldspar cleavage. Notable localities include Oregon (USA), India, Norway, Canada, and Madagascar.
