Rock Identifier
Sunstone (Oligoclase (Plagioclase Feldspar) - (Na,Ca)(Si,Al)4O8 with Hematite or Copper inclusions) — mineral
mineral

Sunstone

Oligoclase (Plagioclase Feldspar) - (Na,Ca)(Si,Al)4O8 with Hematite or Copper inclusions

Hardness: 6-6.5 on the Mohs scale; Color: Orange, reddish-brown, or golden-yellow; Luster: Vitreous to pearly; Crystal Structure: Triclinic; Characteristics: Exhibits aventurescence (a metallic glitter) caused by tiny plate-like inclusions; Specific Gravity: 2.62-2.67.

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

Hardness: 6-6.5 on the Mohs scale; Color: Orange, reddish-brown, or golden-yellow; Luster: Vitreous to pearly; Crystal Structure: Triclinic; Characteristics: Exhibits aventurescence (a metallic glitter) caused by tiny plate-like inclusions; Specific Gravity: 2.62-2.67.

Formation & geological history

Formed in igneous environments, typically within basaltic lava flows or pegmatites. The aventurine effect is caused by the exsolution of copper or hematite crystals as the magma cools and solidifies.

Uses & applications

Primary use is in jewelry as gemstones (cabochons or faceted). It is also highly valued by mineral collectors for its unique optical properties and is occasionally used in decorative carvings.

Geological facts

Also known as 'Heliolite,' sunstone was a legendary navigational tool for Vikings, possibly acting as a 'sunstone' polariscope. Oregon Sunstone is a unique variety featuring copper inclusions and is the official state gemstone of Oregon, USA.

Field identification & locations

Identify in the field by its distinct 'schiller' effect or glittery internal reflections when tilted under a light source. Commonly found in Oregon (USA), Norway, Tanzania, and India. Collectors should look for vibrant colors and strong aventurescence.

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