dioptase

noun

di·​op·​tase

dīˈäpˌtās,

-āz

plural -s

: a mineral CuSiO₂(OH)₂ consisting of hydrous copper silicate and occurring in emerald-green crystals and massive (hardness 5, specific gravity 3.47)

Word History

Etymology

French, probably from Late Greek dioptos transparent (from Greek dia- + optos visible, from opsesthai to be going to see) + French -ase (as in euclase)

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