Sunstone: Oregon's Aventurescent Feldspar

History

The captivating allure of sunstone has intrigued people for centuries. One of the earliest recorded instances of this gem's appeal dates back to the 16th century when Pope Clement VII was said to possess a sunstone featuring a "golden spot that moved in relation to the heavens". Although sunstone has been valued and traded by Native Americans in the Pacific Northwest for a long time, it is a relative newcomer to the broader gem buying public. Oregon officially declared it its state gemstone in 1987. In the realm of birthstone mythology, sunstones are considered the phenomenal birthstone for those born on Sunday.

Gemstone Mineral Origins

Sunstone is a member of the feldspar group of minerals. It can be found in various locations, including the United States, Mexico, China, Namibia, and Madagascar. Oregon sunstone, specifically, is a variety of labradorite, which is part of the plagioclase feldspar solid-solution series. The chemical composition of Oregon sunstone is about 32% albite (NaAlSi3O8) and 68% anorthite (CaAl2Si2O8). What makes Oregon sunstone unique is the presence of copper inclusions, which can give the gem a shimmering effect known as aventurescence or schiller. The schiller effect is caused by flat, reflective inclusions. While other feldspar sunstones may have hematite or goethite inclusions, Oregon sunstones are the only ones with copper inclusions. These copper inclusions are natural and not the result of any enhancements or treatments. Oregon sunstone is sourced from basalt flows. Most of the material is mined on private claims, but there is also a public Sunstone Collection Area in Lake County, Oregon.

The 4 C's

Colour

Colour is the most significant factor when assessing the quality of a sunstone. Sunstones occur in a wide variety of colours, including shades of pink, tan, orange, yellow, green, blue-green, red, and clear. Some stones are bicoloured or tricoloured, and a very few even display colour change. The most sought-after sunstone colours are deep red, deep green, and intensely bicoloured. Red Oregon sunstones are sometimes marketed as "spinel red" because their vivid hue can rival that of spinel and ruby. The best greens are very rare and may be even more costly than the best reds. Some sunstones display a phenomenon called pleochroism, which means that they can display different colours when viewed from different angles.

Clarity

All Oregon sunstones have a unique sheen caused by copper inclusions. Even if these inclusions aren't large enough to create a visible aventurescence, they still contribute to the gem's overall appearance. The presence of copper inclusions is a key identifier of Oregon sunstone. Some stones may have visible schiller inclusions of copper and lead, which can range from an iridescent shimmer to a dull and lifeless look. Lower quality stones may have bold inclusions or appear muted.

Carat

Sunstones come in a wide range of sizes. Smaller stones under one carat are frequently cut into calibrated sizes for standard jewellery mountings. Larger faceted stones are less common, but gem carvers often use larger, non-facet-grade material to create unique pieces. Larger stones with intense colour may be quite valuable.

Cut

Sunstone is a versatile material that is cut into a variety of shapes. The cut of a sunstone can be a key contributor to its overall appearance. Cutters often design unique cuts to highlight the gem's unique colour and optical effects. Fine Oregon sunstones respond very well to faceting, while lower-quality stones are often shaped into cabochons or beads.

Be Aware of

Enhancements

Oregon sunstone is not known to be enhanced or treated. It acquires its copper inclusions naturally. However, other feldspar sunstones from other regions might be enhanced by adding copper through heating and pressure treatments.

Simulants

Be cautious of goldstone, a synthetic material made of glass with copper inclusions that is often used as a simulant for sunstone. A gemmologist will be able to easily distinguish a natural sunstone from goldstone.

Synthetics

Oregon sunstones have not been synthesised.

Final Thoughts

Buying Tips

Be wary of purchasing Oregon sunstones online due to the challenges of accurately photographing their pleochroism, which is the display of two or three distinct colours when viewed from different angles. Also, remember that dealers often price their inventory based on beauty, which can be quite subjective. It is important to look for a reputable dealer, preferably one with a physical retail location. For structured per-carat pricing across schiller, dichroic, and bi-colour tiers, see the Market Bands view on the Gemius species page.

Jewellery Care

Oregon sunstones are best suited for jewellery that does not experience heavy wear, such as pendants, earrings, and brooches, due to their hardness of 6 to 6.5 on the Mohs scale. The best cleaning method for sunstones is warm, soapy water and a soft brush. Avoid mechanical cleaning methods like ultrasonic systems and steam. Be careful not to scratch the gem by storing it away from other jewellery.

Sources

Cited gemological sources
Authority	Title	URL
GIA	Gemological Institute of America, Sunstone encyclopedia + quality factors	gia.edu/sunstone
IGS	International Gem Society, Sunstone buying guide + Sunstone value, price, and jewelry information	gemsociety.org/article/sunstone-jewelry-and-gemstone-information
AGTA	American Gem Trade Association, Sunstone reference	agta.org/gemstones/sunstone

Frequently asked questions

What is Oregon sunstone and why is it special?

Oregon sunstone is a copper-bearing variety of labradorite feldspar found in basalt flows, and it is the only sunstone colored by natural copper. That copper produces its warm glow and its range of red, green, and bicolor stones. It became Oregon's state gemstone in 1987 and is prized as an all-natural American gem.

Is all sunstone natural?

Oregon sunstone is entirely natural, with no treatment involved. Material from other sources is another matter, since some feldspar is diffusion treated with copper under heat and pressure to imitate the Oregon look, and that must be disclosed. Goldstone, the copper flecked glass often confused with sunstone, is wholly man made.

What makes sunstone shimmer?

The shimmer is called aventurescence, or schiller. Tiny flat, reflective inclusions inside the feldspar catch and bounce light, creating a metallic glitter. In Oregon sunstone those inclusions are natural copper, which is unique to that source. The effect ranges from a subtle glow to bold sparkle depending on the size and density of the inclusions.

Why is sunstone hard to judge from online photos?

Sunstone is often pleochroic and shows different colors from different angles, and its copper schiller flashes with movement, which a single photo cannot capture. Color and sparkle that look one way on screen can look quite different in hand. Buy from a reputable seller, ideally one you can view in person.

How can I tell real sunstone from goldstone?

Goldstone is a man-made glass packed with copper flecks, often mistaken for sunstone, but it shows an unnaturally even, dense sparkle. Real sunstone has natural, irregular copper inclusions and true pleochroism. A gemologist separates the two easily. If a sparkly orange stone looks too perfectly glittery and cheap, suspect goldstone.

Is Oregon sunstone treated?

No. Oregon sunstone gets its color and copper shimmer entirely from nature, with no heat or diffusion involved, which is a real selling point. Be aware that some feldspar sunstones from other regions are treated by adding copper through heat and pressure. For Oregon material, the stone is exactly as it came from the ground.

What sunstone color is most valuable?

Deep red, deep green, and strongly bicolor stones are the most sought after. The vivid reds are sometimes marketed as spinel red because the hue can rival spinel or ruby, and the finest greens are rarer still and can cost even more than the best reds. Strong, clean color drives the price.

Is sunstone rare?

Plain shimmering sunstone is common and cheap. Copper bearing Oregon sunstone in strong red or green, and especially bicolour stones, is genuinely scarce, since it comes from a handful of small deposits in one American state. Those are the stones that carry real prices, and they are hard to source.

Is sunstone valuable?

It ranges enormously. Ordinary pale sunstone sells for a few dollars per carat, while fine deep red or green Oregon material with strong clarity reaches several hundred dollars per carat, and top bicolour stones go higher. Colour saturation and the quality of the schiller drive nearly all of that spread.

Is sunstone durable enough for a ring?

With some care. Sunstone is moderately soft at 6 to 6.5 on the Mohs scale, so it scratches more readily than harder gems. It is best in pendants, earrings, and brooches, or a protected ring setting for gentle wear. Clean it with warm soapy water and a soft brush, and avoid ultrasonic and steam cleaners.

Can sunstone get wet?

Yes, briefly. Water alone does not harm feldspar, so hand washing is fine. The caution is that sunstone is 6 to 6.5 on the Mohs scale with two cleavage directions, so remove it before swimming or any impact. Never use ultrasonic or steam cleaning, which act on those cleavage planes.

Does sunstone fade in sunlight?

No. The shimmer is aventurescence, produced by reflective metallic inclusions inside the stone rather than by a pigment, so light cannot fade it. The underlying body colour in Oregon material comes from copper held in the feldspar structure and is equally stable. Dyed imitations, by contrast, can fade.

Is sunstone only found in Oregon?

No, but Oregon is the only source of copper coloured sunstone. Feldspar showing aventurescence is also mined in India, Tanzania, Norway, Russia, and Canada, and India supplies much of the inexpensive orange material in commercial jewellery. Only the Oregon stones get their colour from natural copper.

What does sunstone symbolise?

Sunstone has been read as a solar stone across Norse and later European tradition, associated with warmth, light, and vitality, which follows straightforwardly from its glitter. A separate Norse account describes a solarsteinn used for navigation, though that reference most likely describes iolite rather than this stone.