Quartz has attracted attention from the earliest times; waterclear crystals were known to the ancient Greeks as krystallos—hence the name crystal, or more commonly rock crystal, applied to this variety. The name quartz is an old German word of uncertain origin first used by Georgius Agricola in 1530.
Industrial sand and gravel, often called "silica," "silica sand," and "quartz sand," includes sands and gravels with high silicon dioxide (SiO2) content. These sands are used in glassmaking; for foundry, abrasive, and hydraulic fracturing (frac) applications; and for many other industrial uses. The specifications for each use vary, but silica resources for most uses are