Mineral Class: Oligoclase, Microcline
Crystal System: Triclinic
Hardness: 6 - 6.5
Diaphaneity: Translucent, Transparent
Colors: Red, Pink, Orange, Brown, Black
Source: Canada, Greece, India, Norway, and USA
Sunstone is a variety of feldspar, which when viewed at certain angles, has a spangled appearance. The optical effect appears to be due to reflections from inclusions of red copper, in the form of minute scales, which are hexagonal, rhombic, or irregular in shape, and are disposed parallel to the principal cleavage-plane. These inclusions give the stone an appearance something like that of Aventurine, hence sunstone is known also as "Aventurine-feldspar". The optical effect called schiller 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.
The feldspar which usually displays the Aventurine appearance is oligoclase, though the effect is sometimes seen in orthoclase: hence two kinds of Sunstone are distinguished as "oligoclase sunstone" and "orthoclase sunstone". It has been found in Southern Norway, Sweden, various US states and on some beaches along the mid-coast of South Australia. In 1987, the Oregon State Legislature designated Oregon Sunstone as its state gemstone.