Sunstone
Feldspar var. Sunstone (Oligoclase or Andesine) · Semi-Precious Gemstone
Crystal System
Triclinic; typically occurs as massive, granular, or water-worn pebbles as seen in the specimen.
Mineral Group
Silicates; Tectosilicate (Feldspar Group)
Chemical Formula
(Na,Ca)[Al(Si,Al)Si2O8] with inclusions of Hematite (Fe2O3) or Copper (Cu)
Formation Process
Igneous formation; crystallizes from cooling magma where trace metallic inclusions (copper or hematite) exsolve during cooling to create schiller.
About This Crystal
The specimen is a translucent to opaque reddish-orange stone with a vitreous to pearly luster. It exhibits a characteristic metallic glitter caused by tiny plate-like inclusions.
Physical Characteristics
Color: Orange-brown; Streak: White; Cleavage: Two directions at nearly 90 degrees; Fracture: Uneven to conchoidal; Specific Gravity: 2.62–2.67; Fluorescence: Usually inert.
Optical Properties
Refractive Index: 1.537–1.553; Birefringence: 0.007–0.010; Optical Phenomenon: Aventurescence (schiller effect) caused by light reflecting off internal mineral platelets.
Hardness & Durability
Origin Region
Notably Oregon (USA), Norway, Tanzania, India, and Madagascar. Often found in basaltic lava flows or pegmatites.
Hardness & Durability
Mohs Hardness: 6.0–6.5; Toughness: Poor to fair due to perfect cleavage; suitable for jewelry but requires care against hard knocks.
Care & Maintenance
Avoid ultrasonic and steam cleaners. Clean with warm soapy water and a soft brush. Store separately to avoid scratches from harder gems like quartz or sapphire.
Rarity & Value
Common to Uncommon; Oregon Sunstone with copper is highly prized. Value is determined by the intensity of 'schiller' and color saturation.
Special Characteristics
Aventurescence: A glittering effect caused by reflections from inclusions of hematite (in Norwegian/Indian types) or copper (in Oregon types).
Lore & History
Historically linked to Viking navigation (the legendary 'sunstone' was likely a polarizing feldspar or calcite). Symbolically associated with solar energy, vitality, and leadership.