[shuh-toi-uh
nt] 
| 1. | changing in luster or color: chatoyant silk. |
| 2. | Jewelry. reflecting a single streak of light when cut in a cabochon. |
| 3. | Jewelry. a cabochon-cut gemstone having this reflected streak, as a chrysoberyl cat's-eye. |
chatoyance
the property of some minerals to exhibit a wavy, luminous band with a silky lustre, reminiscent of the eye of a cat, in the centre of a cabochon-cut (polished, with a rounded, unfaceted convex surface) stone. The effect, caused by parallel fibres or by oriented imperfections or inclusions within the stone, is typical of cat's-eye, tigereye, satin spar, and bronzite. The fibres, imperfections, or inclusions are oriented along a crystallographic axis; it is this same kind of orientation, but along three axes, that accounts for the asterism of star sapphire and ruby.
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