Sunstone is a kind of translucent to transparent feldspar exhibiting bright metallic flashes when light interacts with tiny plate-like mineral inclusions within the stone. A brilliant spangled appearance when sunstone is viewed from certain directions has led to its use as a gemstone. The optical effect appears to be due to reflections from inclusions of red copper.
These inclusions give the stone an appearance something like that of aventurine, hence sunstone is known also as "aventurine-feldspar." The optical effect called "shiller" and the color in Oregon sunstone is due to copper. The middle part of this crystal sparkles, and usually the color is darkest in the middle and becomes lighter toward the outer edges.
Sunstone was not common until recently. It has been found in Southern Norway, where masses of the sunstone occur embedded in a vein of quartz. Other locations include Lake Baikal area in Siberia, Australia, Canada, China, Congo, India, Mexico, Sri Lanka, Tanzania, and several United States localities: in Pennsylvania, Oregon, North Carolina, Virginia. Sunstone is the official gemstone of Oregon.
Sunstone has been known for at least a few hundred years: sunstone deposits near Lake Baikal in Russia were mined in the early 1800s, and deposits in southern Norway were mined in the late 1800s. The sunstone deposits of Oregon were discovered by Native Americans who collected the gems, treasured them, traded them widely and sometimes buried their dead with a small bag of stones.
Sunstone is also known as "heliolite" and more commonly "aventurescent feldspar." It is cut into cabochons, beads, and small sculptures. The most transparent pieces are used to produce faceted stones. Sunstone is popular with innovative jewelry designers and is especially popular in the geographic areas where it is commercially mined. It is not a gemstone that is seen in every jewelry store, and many jewelry buyers have never witnessed its aventurescence. However, once a person is given a demonstration of sunstone's aventurescence, they often want to try it and are fascinated.
Some artisans use sunstone for small carvings and sculptures. Material up to three inches in size has been found and some of these large stones are used for carving. Sunstone beads are also popular. As a bead, sunstone displays aventurescence from both sides of the included copper platelets.
