Chatoyancy
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In gemology, chatoyancy, also called chatoyance or the cat's-eye effect, is an optical phenomenon in which a narrow, luminous band of reflected light appears across the surface of certain gemstones. T
Tiger's eye
A tropical veneer exhibiting a very high chatoyancy
Tiger's eye
A cabochon yellow-green quartz showing the cat's-eye effect.
Asterism (gemology)
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An asterism is a star-shaped concentration of light reflected or refracted from a gemstone. It can appear when a suitable stone is cut en cabochon.
Chatoyancy
…Gemology Asterism (gemology) – Star-shaped reflection Optical phenomena – Observable events that result from the interaction of light and matter…
Asterism on the surface of a blue star sapphire.