Meaning

noun a translucent mineral consisting of hydrated silica of variable color; some varieties are used as gemstones

originIn Florio’s A World of Words 1598 as opale, from French opale, from Latin opalus, from Byzantine Greek ὀπάλλιος (opállios), from Sanskrit उपल (upala, “gem, stone”), from उपरि (upári, “the upper millstone”). Distantly related to over.

Etymology from Wiktionary, CC BY-SA 3.0