means A hard, crystalline mineral made of silicon dioxide, found everywhere from beach sand to mountain veins, and prized for keeping precise time in watches.

from From German 'Quarz,' which mining folk of central Europe used for the stubborn crystals they dug up. The German word itself is older and murky — possibly traced back to a West Slavic root like Czech 'tvrdý' (hard) or a related word for a hard, knotty thing — but the trail goes cold, so its deeper ancestry is honestly uncertain.