Gemological knowledge

Sunstone group

Feldspar gems that show aventuresence are called sunstones. They range from opaque through translucent to nearly transparent, depending on the locale, the inclusions and their density. Until recent decades the world knew sunstone only as an opaque coppery material from India. These pieces superficially look a lot like goldstone glass.

At present, the most popular form of sunstone is that from Oregon, USA, which ranges from straw colored transparent stones without aventurescence to transparent pieces in a range of body colors both with and without copper platelets. The metallic shimmery display is commonly referred to as "shiller", although technically that term is more appropriate for the displays seen in Labradorite and moonstone.

The most recent aventurescent feldspar to make a splash in the market, is that from Tanzania, which has hematite and/or copper inclusions. Both transparent and translucent pieces are available and in the best specimens the phenomenon is multi-colored.