Quartzite is a very hard rock composed predominantly of an interlocking mosaic of quartz crystals. The grainy, sandpaper-like surface is glassy in appearance. Minor amounts of former cementing materials, iron oxide, silica, carbonate and clay, often migrate during recrystallization, causing streaks and lenses to form within the quartzite. To be classified as a quartzite by the British Geological Survey, a metamorphic rock must contain at least 80% quartz by volume Parameters Percentage Silica (SiOâ??) 97.00% Alumina (AlO) 1.00% Moisture 1.00% Size 10 to 40 mm, 20 to 70 mm, 40 to 80 mm Origin Maharashtra, India.