Geological processes have occasionally deposited sands composed of nearly 100% quartz grains. These deposits are identified and produced as sources of high-purity silica sand, which is essential for the glassmaking industry. Quartz sand is utilized in the production of container glass, flat plate glass, specialty glass, and fiberglass.
High-purity quartz sandstone, known as quartz glass sand, is ideal for manufacturing high-quality glass. "Glass sand" refers to sandstone almost entirely made of quartz grains. Pictured is a specimen of the Oriskany Sandstone from Hancock, West Virginia. In some locations, the Oriskany is over 99% pure quartz. While much of it is used for container glass, some is selected for making lenses for the largest telescopes. The specimen measures about four inches (ten centimeters) across.
Hydrophilic Silica