Sunstone

Sunstone is a gem-quality feldspar famous for aventurescence, a glittering, spangled sheen produced by light reflecting off tiny plate-like inclusions within the stone. The effect gives the gem a warm, sunlit shimmer that inspired its name.

Sunstone can be a plagioclase feldspar (such as the copper-bearing Oregon Sunstone) or an orthoclase feldspar. Body colors range from pale champagne to rich orange, red, and even green or bicolor in the prized Oregon material.

Oregon Sunstone is notable for being colored by metallic copper, which also produces its sparkle, and is the state gemstone of Oregon.

Sunstone forms as a feldspar within igneous rocks. Oregon Sunstone crystallizes in basalt lava flows, where copper from the magma becomes incorporated as microscopic platelets that give both color and aventurescence.

Other sunstones form in igneous and metamorphic rocks where tiny inclusions of hematite or goethite create the reflective glitter. The inclusions align along crystal planes, so the sparkle shifts as the stone is turned.

Sources include Oregon (USA) for copper-bearing material, plus India, Norway, Russia, Canada, and Tanzania for other varieties.

The defining feature is aventurescence: a metallic, glittery flash from internal platelets, best seen when rotating the stone under light. Body color is typically warm orange, golden, or reddish.

Sunstone has a hardness of 6-6.5, two directions of cleavage typical of feldspar, a vitreous luster, and a white streak. The sparkle comes from inside the stone, not the surface.

The main man-made look-alike is goldstone, a glittery glass with copper flecks; goldstone shows a uniform, dense sparkle and gas bubbles, while natural sunstone has feldspar cleavage and more natural, scattered glints. Aventurine quartz is harder and green.

Sunstone is faceted and cabbed for rings, pendants, and earrings, with fine Oregon copper-bearing stones reaching high values, especially in red and green or bicolor hues. Its sparkle makes it a distinctive jewelry gem.

It has been used decoratively for centuries and was reportedly used by Vikings, though the famous "sunstone" navigation legend more likely referred to a different mineral.

Metaphysically, sunstone is linked to warmth, vitality, and optimism. Value depends on color saturation, strength of aventurescence, clarity, and, for Oregon material, the presence of red or green and a copper schiller.