Rock Identifier
Sunstone (Oligoclase (Plagioclase Feldspar) with inclusions of Hematite or Copper) — gemstone
gemstone

Sunstone

Oligoclase (Plagioclase Feldspar) with inclusions of Hematite or Copper

Hardness: 6.0-7.2 (Mohs); Color: Orange, reddish-brown, or yellow; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in two directions; Features aventurescence (metallic schiller).

Hardness
6
Color
Orange, reddish-brown, or yellow
Luster
Vitreous to pearly
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Physical properties

Hardness: 6.0-7.2 (Mohs); Color: Orange, reddish-brown, or yellow; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in two directions; Features aventurescence (metallic schiller).

Formation & geological history

Forms in igneous rocks like basalt flows or plutonic rocks through slow cooling, allowing copper or hematite platelets to precipitate within the feldspar lattice. Most abundant in Oregon (basalt) and Norway (pegmatite).

Uses & applications

Primarily used as a semi-precious gemstone for jewelry (cabochons and faceted stones) and for lapidary arts and metaphysical collecting.

Geological facts

Oregon Sunstone is the official state gemstone of Oregon. The metallic glitter effect is known as 'schiller' and is caused by light reflecting off tiny plates of copper or hematite inside the stone.

Field identification & locations

Identify by looking for the 'aventurescent' flash when rotating the stone under light. Look for its characteristic cleavage planes and distinct orange-to-red metallic sheen. Common in Oregon, USA, and parts of India and Norway.