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Sunstone

Last updated: April 2026

A plagioclase feldspar (typically oligoclase or andesine) displaying aventurescence — a metallic shimmering or spangling caused by flat metallic inclusions. Oregon sunstone (often andesine-labradorite, RI up to ~1.568) may show red, green, or bicolor zones. Indian sunstone (oligoclase) shows a golden glitter from hematite/goethite platelets. Copper-bearing Oregon sunstones are natural and untreated.

Sunstone has a specific gravity of 2.63 and a refractive index of 1.537–1.572, with a Mohs hardness of 6.0–6.5. It is biaxial −.

Physical & Optical Properties

RI Range1.537–1.572
SG Range2.62–2.65
SG Typical2.63
Hardness (Mohs)6–6.5
Crystal SystemTriclinic
Optic CharacterDR Biaxial (−)
Birefringence0.010
Dispersion0.012
Fluorescence LWWeak orange
Fluorescence SWInert
Chelsea FilterInert
PleochroismWeak
ColorsYellow Orange, Red Pink, Colorless, Green
SpeciesFeldspar
VarietyPlagioclase (Oligoclase / Andesine)
Yellow OrangeRed PinkColorlessGreen

AmazoniteLabradoriteMoonstoneRainbow Moonstone

Key Differentiators

Treatments

Price Context

Natural — low ($/ct)$10
Natural — high ($/ct)$300
NotePer carat; Oregon sunstone (bicolor, deep red, or large copper inclusions) commands significant premium; Indian material more common and less expensive

Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.

Measurement Guides

How to Identify a GemstoneHow to Measure Specific GravityHow to Use a RefractometerUV Fluorescence Testing

Identifying a sunstone? GemID walks through these tests in order — RI, SG, fluorescence, and more.

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Studying for the GIA, FGA, or FEEG practical? Sunstone is one of the 130 species in GemID’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.

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