dioptasePronunciation: /dʌɪˈɒpteɪz/Definition of dioptase noun [mass noun] a rare mineral occurring as emerald green or blue-green crystals. It consists of a hydrated silicate of copper. Origin: early 19th century: from French, formed irregularly from Greek dioptos 'transparent'dioptase in other Oxford dictionaries Definition of dioptase in the US English dictionary
