Rock-crystal
A common name for the finest and purest quartz or transparent, crystallized silica. The pebble lenses for spectacles, etc., are made from rock-crystal. See QUARTZ; SILICA.
Twelve hundred entries from the golden age of cast metal — how bells are founded, why brass is not bronze, what a cupola melts and a core withstands — by Simpson Bolland, the trade's great teacher.
A common name for the finest and purest quartz or transparent, crystallized silica. The pebble lenses for spectacles, etc., are made from rock-crystal. See QUARTZ; SILICA.