Oregon sunstones are a unique and visually captivating variety of feldspar known for their copper inclusions, which give them a distinctive glittering effect known as schiller.
They’re mostly found in southeastern Oregon, particularly in Lake County, which is famous for sunstone deposits. Oregon sunstone can range in color from water-clear through pale yellow, soft pink, and blood red to deep blue and green, making each stone distinct and unique from the next.
The presence of copper particles is what sets Oregon sunstones apart from other types of feldspar. The copper can be dispersed within the stone in various ways, sometimes concentrated in certain areas or scattered uniformly, which affects the light reflection and adds to the depth and intensity of the stone’s appearance.
Depending on the concentration and orientation of these copper inclusions, the stones can exhibit an aventurescent quality, sparkling with metallic reflections.
Oregon sunstone is relatively hard, ranking about 6 to 6.5 on the Mohs scale, which makes it a great stone to use in jewelry. It’ i’s especially popular in rings, earrings, and pendants that highlight its unique color and schiller.
Legally designated as the official state gemstone of Oregon, sunstones hold a special place in local culture and gem markets. They’re mined in a few large public collection areas as well as through private claims where collectors can pay to dig for their own sunstones.
These gemstones are not only prized for their beauty and rarity but are also valued for being one of the few gemstones mined commercially in the United States without significant environmental disruption.
Oregon Sunstone Physical Characteristics
Classification: Variety of feldspar, specifically a gem-quality plagioclase feldspar
Chemical Composition: (Ca, Na)Al₁-₂Si₃-₂O₈ (calcium sodium aluminum silicate)
Color: Ranges from colorless to yellow, pink, red, green, blue, and even coppery hues. The presence of copper inclusions often gives it a unique aventurescent effect known as schiller.
Streak: White
Hardness: 6-6.5 on the Mohs scale
Cleavage: Perfect in one direction
Fracture: Conchoidal to uneven
Luster: Vitreous to pearly
Transparency: Transparent to translucent
Crystal System: Triclinic
Formation and Geology
Oregon Sunstone forms in the basalt flows of the volcanic highlands of southeastern Oregon. It crystallizes in lava flows and can be found in cavities within the basalt where it forms well-shaped crystals. The distinctive copper inclusions in Oregon Sunstone, which can range from microscopic specks to larger platelets, are a result of the presence of copper in the basalt. These inclusions are responsible for the stone’s aventurescence and unique color variations.
Variety of Colors and Types
Oregon Sunstone is prized for its diverse range of colors and its distinctive aventurescence, which creates a sparkling effect within the stone. This phenomenon is particularly pronounced in stones with a high concentration of copper inclusions.
They can exhibit a range of colors from clear and pale yellow to deep reds and greens. Some rare specimens display a dichroic effect, showing different colors when viewed from different angles. The three main types based on color and transparency include clear, schiller (showing copper flakes), and dichroic. The stone’s transparency and play of light make it a popular choice for fine jewelry.
Public Collecting Sites
The most famous location for collecting Oregon sunstones is the public area in the Rabbit Basin. This is a free, public collection area managed by the Bureau of Land Management (BLM) where enthusiasts can dig for sunstones. There are also several privately-owned mines that allow the public to dig for a fee, providing opportunities to find higher quality stones.
Gemstone Quality and Jewelry Making
The quality of sunstones varies greatly, from gem-quality stones that can be faceted into beautiful jewelry, to lower grade stones that might be better suited for other decorative purposes. Factors affecting the gem quality include the presence and effect of schiller, color intensity, and clarity.
Collecting Ethics and Practices
It’s important for rockhounds to follow ethical collecting practices. This includes respecting land regulations, obtaining necessary permits, and practicing the “leave no trace” principles to preserve the site for future collectors.
