Sunstone is also called aventurine feldspar (a variety of oligoclase). This gemstone varies from golden to orange to red-brown, and can be transparent or translucent. Sunstone is metallic-looking due to sparkling red, orange or green crystalline inclusions (these are hematite or goethite crystals).
Sunstone has a beautiful glittering sunlight effect as a result of its tiny metallic inclusions. The copper or pyrite inclusions cause sparkling flashes of light as millions of particles playfully interact with light. This feature is known as "Schiller" or “Aventurescence? Sunstones are nearly always cut as cabochons to reflect this phenomenon, but the deeper colors may also be faceted to exhibit their superior luster.
Sunstone is formed and crystallized in lava flows. Sunstones range in color from water clear through pale yellow, soft pink, and blood red to deep blue and green. Some of the deeper colored gems have bands of varying color while others exhibit Pleochroism, showing two different colors when viewed from different directions.