Chatoyancies

Part of speech: noun

Definitions

1. The visual phenomenon of a shifting, luminous line appearing across a gemstone or other surface, especially when light reflects in certain angles
2. The quality found in certain materials where they exhibit a band of light resembling a cat's eye, often seen in specific gems
3. A characteristic of specific stones where a distinct light band moves with changes in viewing position, enhancing their aesthetic appeal

Etymology: "Chatoyancies" is the plural of "chatoyancy," a noun for the shimmering, cat's-eye effect seen in certain gems and fibres. The base word is "chatoyant," which is itself borrowed from French "chatoyant," the present participle of "chatoyer," meaning "to shimmer like a cat's eye." That French verb comes from "chat," cat, so the word's core image is the eye of a cat catching the light. The suffix "-cy" is the English ending that turns an adjective into a noun denoting a quality or state, as in "fluency" or "constancy." Adding it to "chatoyant" produced "chatoyancy" for the quality of showing that moving band of light, and the plural form simply counts separate instances of it across several stones or surfaces.