= Asterism (gemology)
{wiki=Asterism_(gemology)}
Asterism is a phenomenon observed in certain gemstones that produces a star-like pattern of light on their surface, typically when viewed under a direct light source. This optical effect is caused by the presence of needle-like inclusions within the stone, often composed of the mineral rutile, which are oriented in specific directions. When light strikes these inclusions, it reflects and refracts, creating a star shape that usually radiates from a central point.
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