Sunstone: meaning, properties and lore

The mineral

Sunstone is a member of the feldspar group of minerals, and both orthoclase and plagioclase feldspar species include a sunstone variety.¹²

Oligoclase and labradorite sunstone are a solid solution between NaAlSi₃O₈ and CaAl₂Si₂O₈. Sunstone is An70 labradorite, a high calcic plagioclase feldspar, and Oregon sunstone has a composition of about 70% anorthite and 30% albite.¹⁶⁷

Sunstone has a Mohs hardness of 6.0 to 7.2. Red Oregon sunstone is less hard than spinel or ruby, although its vivid hue rivals those stones. The stone is durable enough for jewelry and daily wear, but rough handling should be avoided.¹⁸³

The refractive index of orthoclase sunstone is 1.518 to 1.526, of oligoclase sunstone 1.537 to 1.547, and of labradorite sunstone 1.559 to 1.568.¹

Sunstone occurs in yellow, green, red, red-brown and colorless. The glitter, called aventurescence, is caused by flat, reflective inclusions that can be hematite, copper or some other mineral.¹³²⁸

The aventurescence is caused by inclusions identified as pure native copper, which are often called schiller. Only about 20 ppmw of exsolved metallic copper can produce saturated colors in mostly transparent Oregon sunstone crystals. Microprobe analyses of colorless, red and green sunstone did not reveal an obvious causative mechanism for the colours, and researchers are investigating whether intervalence charge transfer, possibly involving colloidal copper, is responsible.⁶⁷⁴

Oregon sunstone is found in South Central Oregon, in the high-desert area, and is mined at the Plush, Oregon mining area and the Ponderosa mine. It occurs as phenocrysts in highly porphyritic basalt flows in eastern Oregon, and Oregon is the only verified occurrence of gem-quality copper-bearing sunstone. Several mining claims in Oregon today produce material for mass marketers, carvers and high-end jewelry designers.³²⁵⁷⁴

Sunstone crystals from the Sunstone Butte mine are often larger and less fractured than elsewhere, with some exceeding 10 cm in length. Oregon sunstone has poorly developed cleavages and few inclusions or twins because of the disordered structure from a fast cooling rate. The crystal's low triclinic symmetry adds complexity to how light interacts with its copper particles.⁷⁴

Oregon sunstone is a natural and untreated product of the United States, and its colors do not result from treatment. Pale feldspar from other areas might be enhanced in color, and Woodmark stockpiles colorless and yellow Oregon sunstone because it is easily treatable. Large faceted sunstones are uncommon, and gem carvers often use non-facet-grade material for unique creations.¹⁸²⁷

History and lore

In the early 1800s sunstone was a little-known, rare and costly gemstone. It became somewhat more widely recognized and less expensive after finds in Norway, Siberia and other parts of the world. Gemologists have called sunstone's aventurescent feldspar by the term aventurine feldspar.²⁵

Andersen (1915) defined the term sunstone as the gem variety of aventurine feldspar showing intense play of light and colors from thin oriented metallic inclusions. Andersen (1917) first documented copper-containing aventurine feldspar, from specimens reportedly from Modoc County, California. Hofmeister and Rossman (1983) first hypothesized that anisotropic colloids could cause the strong pleochroism often seen in green-blue Oregon sunstones.⁴

In the early 1900s there were reports of sunstone finds in ancient lava fields in a desert area called Warner Valley in Oregon. Discoveries of glittery sunstone rough then led miners to establish claims in Oregon.⁵

According to Native American legend, the blood of a wounded great warrior dropped onto pieces of Oregon sunstone, carried his warrior spirit into the stones, and gave them shades of red and sacred power. A museum in Jacksonville, Oregon, includes sunstones in its display of Indian artifacts.⁵

Kunz lists sunstone among the phenomenal gems given to the days of the week, in a list he presents in his book The Curious Lore of Precious Stones.⁹

Gem treatment investigations in the early 2000s found that a material sold as Tibetan sunstone might have been pale andesine from Mongolia treated by copper infusion. Promoted as andesine and purportedly from Congo or Tibet, treated copper-bearing feldspar was later found to be treated. Woodmark purchased the Ponderosa property in 2003.²⁷

Oregon sunstone miners and the market were affected by the early 2000s diffusion of copper into pale feldspar by Asian treaters. Johnston (1991) characterized the Ponderosa labradorite as 70% anorthite and 30% albite, placing it at the labradorite/bytownite boundary.⁷

Birthstone and zodiac links

Sunstone is associated with the modern modern modern zodiac sign Leo and the modern modern modern planetary Sun, according to crystal practitioners, who present this as a modern link.

What crystal practitioners say

Crystal practitioners associate sunstone with the mind and with confidence. Believers say sunstone helps individuals overcome fears and insecurities and promotes self-image and confidence. Practitioners say it is used to clear mental fog and increase focus, and believers hold that its vibrant energy uplifts spirits and brings vitality and enthusiasm.

Believers hold that sunstone shields the aura from negative energies and psychic attacks. This protective view is held by believers within crystal practice, and it sits alongside the chakra view of practitioners who say the stone is used to stimulate and balance the sacral chakra. Practitioners say this supports self-expression, passion and sensuality.

Practitioners charge sunstone by placing it in direct sunlight for several hours, since they say it resonates with the sun's energy. Practitioners' sunlight charging should be weighed against the mineral fact that sunlight or heat can fade the stone.

What testing has found

Ernst states that a scientific proof of any positive effect of crystal healing beyond a placebo effect does not exist, and says feelings of success can be attributed to the strong placebo effect and to believers' cognitive bias. Ernst notes that crystal healing can generally be regarded as harmless and without toxicity.¹⁰

In a 2001 study, British psychologist Christopher French asked 80 volunteers to distinguish genuine crystals from imitations after holding them and meditating. Those who held fake stones reported impressions much like those who held real ones, which points to the placebo effect as a likely explanation.¹⁰

Ted Kaptchuk, a Harvard Medical School professor, said discarding placebo effects diminishes knowledge of important dimensions of health care. Rigorous scientific research into crystal therapy is lacking, and the scientific community remains skeptical. Natural Oregon sunstones have much lower copper concentrations than diffused feldspars of similar color intensity, according to Sun et al. (2020) and Jin et al.¹¹⁴