German Quarz, from Middle High German twarc, probably from a West Slavic language (compare Czech tvrdý (“hard”), Polish twardy (“hard”), Russian твёрдый (tvjórdyj, “hard”)), from Old Church Slavonic тврьдъ (tvrĭdŭ, “firm”), from Proto-Slavic *tvьrdъ.
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- (mineralogy) The most abundant mineral on the earth's surface, of chemical composition silicon dioxide, SiO2. It occurs in a variety of forms, both crystalline and amorphous. Found in every environment.