dioptase

noun
di·​op·​tase | \dīˈäpˌtās, -āz\
plural -s

Definition of dioptase 

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

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History and Etymology for dioptase

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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