Sunstone

Sunstone is a feldspar that contains very small, flat metallic platelets (copper, hematite or goethite) that reflect light as glitter. As the stone is turned, these platelets flash in gold, orange and red; the effect is called aventurescence. Most sunstone is plagioclase: the Norwegian and Indian stones are oligoclase, while the Oregon stones, from the US state of Oregon, are copper-bearing labradorite. Rarely, potassium feldspars (orthoclase or microcline) show the same effect.

Jewellery: It is used in cabochons, beads and carvings; faceted stones are also cut from Oregon's large, coloured crystals. Because it has distinct cleavage, it needs protection from knocks. Collecting: Oregon stones showing red and green together, with glittering copper platelets, are sought by collectors. Local symbol: Oregon sunstone has been the state's official gemstone since 1987 and is promoted as an untreated stone mined in Oregon.

It has a hardness of 6–6.5 on the Mohs scale. It can scratch glass; a steel knife scratches it only with difficulty. Its specific gravity is 2.62–2.76 g/cm³.

Its best-known localities: Plush area (Dust Devil and Sunstone Butte mines), Lake County, Oregon, USA; Ponderosa mine area, near Burns, Harney County, Oregon, USA; Tvedestrand, Agder, Norway; Tamil Nadu, India; Lake Baikal area, Siberia, Russia.

Turn the stone in the light and the small, flat platelets inside flash gold, orange or red; the effect is visible from certain angles. The body colour is usually yellow, orange or reddish brown; Oregon stones can be red and green, sometimes both colours in one stone. Its hardness is 6–6.5; with distinct cleavage in two directions (one perfect, one good) it is sensitive to knocks. Copper-diffused “andesine”: in the early 2000s most of the red and green stones sold as “andesine”, said to come from Congo or Tibet, had been coloured by diffusing copper into pale feldspar. They shook trust in Oregon sunstone.

On the “street to diamond” value ladder it sits on step 5 of nine: Ornamental stone. Value depends mostly on colour and glitter: in Oregon stones vivid red or green, bicolour stones with red and green together, and a rich display of glittering copper platelets (schiller) are sought. Because the red and green colours and the schiller are mostly confined to the core of the crystal, large, clean, coloured stones are rare. Cut quality, size and clarity also matter. Because of the copper-diffused “andesine” episode, it is important that a stone is stated to be natural and untreated.

Kunz writes that Eastern peoples believed stones with remarkable light effects (cat's-eye, star sapphire and the like) brought good fortune; when he assigns such stones to the days of the week, Sunday goes to sunstone. Today crystal-therapy sources claim that sunstone gives joy, vitality and optimism and strengthens self-confidence and leadership. The same circles say that sunstone brings luck and abundance. Some sources claim that sunstone helps with seasonal affective disorder, depression and despair, and absorbs anxiety, fear and anger. There is no scientific evidence that sunstone brings joy, luck, vitality or courage. Seasonal affective disorder and depression are medical problems; see a doctor rather than relying on a stone. The “sun” comparison comes from the metallic platelets in the stone reflecting light; no light or energy comes out of the stone itself. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.