Labradorite is a member of a series of sodium and calcium silicate minerals known as plagioclase feldspars. Feldspars are major constituents of rocks and seldom are transparent or attractive enough to fashion into gemstones. Labradorite sometimes forms transparent crystals in volcanic rocks known as basalt. These crystals, called phenocrysts, are usually quite small and pale yellow in color. But in some localities, such as in Oregon, they can be up to several inches across and completely transparent. Gem feldspars with the composition of labradorite are known in the gem trade as sunstone. In Oregon these crystals occur in various colors, including red, orange, yellow, blue-green, green and pink. The colors are due to trace impurities of copper contained within the feldspar crystal structure. Red and green colors are the rarest and most valuable, and sometimes color zoning causes both colors to appear in the same gemstone. Oregon sunstone can be faceted into bright and attractive gemstones. The gemstones pictured, range in size from about 2 to 5 carats, and display the colors that make Oregon sunstones unique in the world.