Sunstone is a plagioclase feldspar, which when viewed from certain directions exhibits a brilliant spangled appearance; this led to its use by the Vikings to locate the Sun for navigational purposes. It has been found in Southern Norway, Sweden and in various United States localities. 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 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.