Sunstone
Oligoclase var. Sunstone (Feldspar variety) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Triclinic; often occurs in massive forms or as part of larger plagioclase crystals with cleavage planes visible.
Mineral Group
Silicates; Tectosilicates (Plagioclase Feldspar group)
Chemical Formula
(Ca,Na)(Al,Si)4O8 with Hematite (Fe2O3) or Copper (Cu) inclusions
Formation Process
Igneous formation; typically crystallizes from cooling magma in pegmatites or basaltic flows, allowing for the exsolution of metallic inclusions.
About This Crystal
A translucent to opaque feldspar characterized by a warm orange to reddish-brown body color. It features a distinct aventurescence (shiller effect) caused by tiny, plate-like inclusions of hematite, goethite, or copper that reflect light.
Physical Characteristics
Color: Orange/Peach/Reddish-brown; Streak: White; Luster: Vitreous to pearly; Cleavage: Perfect in two directions roughly at 90 degrees; Fracture: Uneven to conchoidal; Specific Gravity: 2.62-2.67; Fluorescence: Weak red/orange under UV.
Optical Properties
Refractive Index: 1.532-1.552; Birefringence: 0.007-0.010; Optical Effect: Aventurescence (shiller); Biaxial negative/positive; Pleochroism is usually weak.
Hardness & Durability
Origin Region
Norway (classic Tvedestrand deposits), Oregon (USA), Tanzania, India, and Canada.
Hardness & Durability
Mohs Hardness: 6.0 to 6.5; Toughness: Poor to Fair due to perfect cleavage; brittle stability. Suitable for jewelry with protective settings.
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic or steam cleaners. Store separately to prevent scratching from harder stones like quartz. Sensitive to rapid temperature changes.
Rarity & Value
Common to Uncommon; Oregon Sunstone with copper inclusions is more rare and valuable. Value is dictated by the density of the shiller effect, color saturation, and clarity.
Special Characteristics
Displays aventurescence, a metallic schiller or glittery effect caused by internal reflections from mineral platelets (hematite or copper).
Lore & History
Historically linked to Viking navigation (as a possible 'sunstone' polariscope) and Greek mythology representing the Sun God. In metaphysical lore, it is believed to promote leadership, benevolence, and energy for the Sacral Chakra.