Asterism (general)

Asterism refers to a star-like visual phenomenon that appears on the surface of certain gemstones, commonly quartz. This effect is created by the presence of inclusions, usually of rutile, that reflect light in a way that forms a star shape, typically with three or six rays. Asterism can enhance the beauty and value of stones like star sapphires and star rubies. The effect is best seen under a direct light source, which showcases the star's movement as the stone is rotated. Overall, asterism adds a captivating element to the appearance of certain gemstones.