Aventurine Feldspar

Aventurine feldspar is the gem more commonly called sunstone—a feldspar that displays aventurescence, a glittering, spangled play of metallic-looking flashes caused by countless tiny reflective platelets within the stone.

The host is usually oligoclase (a sodium-calcium plagioclase) and, in the case of Oregon sunstone, labradorite. The sparkle comes from oriented inclusions of hematite, goethite, or—in Oregon material—native copper.

Body colors range from warm orange and reddish-brown to golden and, in copper-bearing stones, can include pink, red, and green. It is a popular, warm-toned gem cut both as cabochons and faceted stones.

Aventurine feldspar forms as plagioclase crystallizing in igneous rocks. During cooling, microscopic platelets of metallic minerals exsolve or are trapped in oriented planes within the feldspar, and light reflecting from these platelets produces the aventurescent sparkle.

Classic Indian and Norwegian sunstone (oligoclase) contains hematite or goethite platelets. Oregon sunstone forms in basalt lava flows and carries native copper inclusions, which can also impart red and green hues through copper coloration.

Major sources include Oregon (USA), India, Norway, Russia, Tanzania, and Canada.

Identify aventurine feldspar by a warm-colored translucent feldspar showing a metallic glitter or schiller when turned in the light. Hardness is about 6-6.5 with vitreous luster and feldspar cleavage.

Distinguish it from aventurine quartz, which is usually green and harder (7) with a green chrome-mica sparkle, and from goldstone, a man-made glass with very regular, dense copper-colored glitter. Sunstone's sparkle is sparser and tied to a feldspar body with cleavage.

Oregon copper-bearing sunstone may show red/green zoning, a helpful diagnostic. Twinning striations and feldspar cleavage confirm the feldspar identity.

Aventurine feldspar (sunstone) is used as a gemstone in rings, pendants, earrings, and beads, cut as cabochons or faceted to show transparency and sparkle. Oregon copper-bearing sunstone is especially valued and is the state gem of Oregon.

Metaphysically, sunstone is associated with warmth, vitality, optimism, and personal power, reflecting its solar appearance; these associations are traditional rather than scientific.

Its cheerful color and shimmer make it a favorite for both fine and artisan jewelry.