•a hard glossy mineral consisting of silicon dioxide in crystal form; present in most rocks (especially sandstone and granite); yellow sand is quartz with iron oxide impurities
From German Quarz, from Middle High German (Central East German) quarz, twarc, from a West Slavic language [compare Polish twardy (“hard”), Czech tvrdý (“hard”)], from Proto-Slavic *tvьrdъ ultimately from Proto-Indo-European *twerH- (“to enclose, grab”).