Sunstone

Sunstone is a beautiful variety of plagioclase feldspar known for its internal metallic flashes, a phenomenon called 'aventurescence'. This sparkling effect looks like tiny golden glitters floating inside the stone. It is often found in warm shades of orange, gold, and red, though more rare green varieties exist. It is a cousin of moonstone and labradorite but shows a completely different optical effect.

Formation & Geology

Sunstone forms in certain types of basalt and pegmatites. The aventurescence is caused by tiny, plate-like inclusions of copper (in Oregon sunstone) or hematite/goethite (in most other varieties). When light hits these microscopic flakes, they reflect like tiny mirrors. The intensity of the sparkle depends on the size and concentration of these inclusions. Oregon sunstone is unique because it is the only variety that contains actual copper.

Physical Characteristics

Like all feldspars, sunstone has a hardness of 6 to 6.5 and two directions of perfect cleavage. It has a vitreous to pearly luster and can be transparent to translucent. It is often cut as cabochons to best show the sparkle, but high-clarity specimens are often faceted. Larger inclusions cause a bold glitter, while very fine inclusions produce a soft, reddish glow called 'schiller'.

Historical Significance

Native Americans in Oregon used sunstone for trade and believed it was formed from the blood of a great warrior. Legend says that Viking sailors used a 'sunstone' (though possibly cordierite or calcite) as a navigation tool to find the sun through clouds. Today, Oregon Sunstone is the official state gemstone of Oregon. It is popular in designer jewelry for its unique, warm appearance that captures the essence of sunlight.

The Viking Compass Legend

According to Norse sagas, Viking navigators used a "Sunstone" (Sólarsteinn) to locate the sun in the sky on cloudy days, allowing them to navigate the open ocean. While the exact mineral is debated (Iceland Spar Calcite or Iolite are also candidates), the optical phenomenon of polarization in Sunstone makes it a plausible candidate for this ancient navigational tool.