moonstone

[ moon-stohn ]
/ ˈmunˌstoʊn /
|

noun

Also called precious moonstone. a semitransparent or translucent, opalescent, pearly-blue variety of adularia, used as a gem.
any of several adularescent feldspars, as certain varieties of albite, labradorite, or oligoclase, used as gems.
(not used technically) any milky or girasol stone used as a gem.

Origin of moonstone

First recorded in 1625–35; moon + stone
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for moonstone

moonstone

/ (ˈmuːnˌstəʊn) /

noun

a gem variety of orthoclase or albite that is white and translucent with bluish reflections
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012