Oligoclase is a species of plagioclase feldspar. The variety used in jewellery is called sunstone or, less commonly, aventurine feldspar. It has reflective inclusions of red, orange, or green platy crystals, which give it a metallic glitter. Sunstone might be faceted or carved – often as cabochons.
Sunstone occurs in metamorphic and igneous rocks in Norway, United States, India, the former USSR, and Canada.