Got a photo? Identify rocks instantly with the Rockby app
Open the appDescription
Sunstone is a captivating gemstone known for its aventurescence, a shimmering optical effect caused by tiny metallic inclusions. It is a variety of oligoclase, a member of the plagioclase feldspar series. The color can range from colorless or yellow to orange, pink, red, and even green, often with a metallic sheen. The intensity and color of the Schiller effect depend on the size, shape, and composition of the inclusions.
How to Identify
- Color
- Typically orange, pink, red, yellow, or colorless, often with a metallic glitter. Can also be green.
- Luster
- Vitreous to sub-vitreous, with a distinct metallic or spangled aventurescence.
- Texture
- Smooth to slightly granular, depending on crystal size and habit.
- Crystal Form
- Usually found as anhedral to subhedral grains in igneous rocks, or as well-formed tabular crystals in pegmatites. Often massive.
- Cleavage
- Perfect in two directions, nearly at right angles (approximately 90 degrees).
- Geological Environment
- Commonly found in mafic igneous rocks (e.g., basalt, gabbro), pegmatites, and some metamorphic rocks. Also found in placer deposits due to its relative hardness and resistance to weathering.
Key Facts
- Hardness: 6 - 6.5 on the Mohs scale
- Specific Gravity: 2.62 - 2.67
- Crystal System: Triclinic
- Color: Colorless, yellow, orange, pink, red, green; often with metallic glitter (aventurescence).
- Luster: Vitreous to sub-vitreous, with aventurescence.
- Transparency: Transparent to translucent.
- Fracture: Uneven to conchoidal.
- Cleavage: Perfect in two directions ({001} and {010}) at nearly 90 degrees.
- Composition: Sodium calcium aluminum silicate, (Na,Ca)(Al,Si)AlSi2O8, with inclusions of hematite, goethite, or copper.
Quick Check
- Color: Orange, pink, red, yellow, or colorless with metallic glitter.
- Luster: Vitreous to sub-vitreous with aventurescence.
- Streak: White
Physical Characteristics
- Crystal Habit: Typically anhedral to subhedral grains, massive, or as tabular crystals.
- Cleavage Type: Perfect in two directions, nearly at right angles.
- Fracture Type: Uneven to conchoidal.
- Tenacity: Brittle.
- Luster Type: Vitreous to sub-vitreous, with aventurescence.
Formation
Sunstone is a plagioclase feldspar, specifically oligoclase, that exhibits aventurescence (a spangled, glittery effect) due to inclusions of hematite, goethite, or sometimes copper. These inclusions are typically small, thin platelets oriented along specific crystallographic planes, reflecting light at various angles to produce the characteristic Schiller effect.
Usage
Primarily used as a gemstone for jewelry due to its unique optical phenomenon. Also collected by mineral enthusiasts.
Age Distribution
Found in various geological ages, typically associated with igneous and metamorphic rocks.
Where to Find
Oregon, USA
Known for its copper-bearing sunstone, which can exhibit a range of colors including green and red, and often displays a strong aventurescence. Found in basalt flows.
Norway
Historically significant source, particularly for oligoclase sunstone with hematite inclusions.
India
Produces sunstone with hematite inclusions, often with a reddish-orange hue.
Tanzania
Known for producing sunstone with a good play of color.
Canada (Quebec)
Some occurrences of sunstone have been reported.
Russia
Ural Mountains region has produced sunstone.
Finding Tips
Look for Igneous Rocks
Sunstone is frequently found in mafic igneous rocks like basalt and gabbro, or in pegmatites. Search in areas with exposed igneous formations.
Examine for Aventurescence
The most distinctive feature is the metallic glitter. Rotate the specimen under a light source to observe the Schiller effect. This is crucial for identification.
Check for Cleavage
Feldspars have characteristic cleavage planes. Look for two perfect cleavages intersecting at approximately 90 degrees.
Consider Placer Deposits
Due to its durability, sunstone can be found in alluvial deposits (riverbeds, gravels) downstream from its primary source.
Similar Rocks
Aventurine Quartz
Quartz (SiO2) with Fuchsite or Hematite inclusions
Also known as: Green Aventurine, Blue Aventurine
Labradorite
Labradorite ((Ca,Na)(Al,Si)AlSi2O8)
Also known as: Spectrolite
Moonstone
Orthoclase or Albite-Orthoclase intergrowth
Also known as: Adularia, Peristerite
Scientific Classification
- Mineral Class
- Silicate
- Group
- Feldspar Group, Plagioclase Series
- Crystal System
- Triclinic
- Chemical Formula
- (Na,Ca)(Al,Si)AlSi2O8 (Oligoclase end-member range: An20-An30), with inclusions of Fe-oxides or Cu.
- Composition
- A solid solution of albite (NaAlSi3O8) and anorthite (CaAl2Si2O8), specifically within the oligoclase range (20-30% anorthite), characterized by microscopic inclusions causing aventurescence.
Explore Sunstone
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.