Quartzite

Characteristics and Origin: Quartzite is a hard rock with an interlocking mosaic of quartz crystals. The surface of quartzite is grainy and glassy in appearance. Quartzite must contain at least 80% quartz by volume for British Geological Survey classification. Quartzite is formed when sandstone undergoes regional metamorphism, with quartz grains recrystallizing. Recrystallized quartz grains in quartzite are roughly equal in size, forming a granoblastic texture. Geographical Occurrence: Quartzite formations can be found in regions across the United States, including Pennsylvania, South Dakota, and Utah. Notable locations with quartzite include the Morenci Copper Mine in Arizona and the La Cloche Mountains in Ontario, Canada. Quartzite deposits are also present in Ireland, the United Kingdom, and continental Europe. Precambrian basement rock in western North America features Paleoproterozoic quartziterhyolite successions. Uses: Quartzite has historical uses in prehistoric stone tools and contemporary applications as decorative dimension stone. It is utilized in highway construction as crushed stone and as a source of silica for silicon production. Quartzite’s hardness and resistance make it valuable for various industrial applications. Increasingly used for kitchen countertops due to its durability and stain resistance. Relationships with Other Rocks: Quartzite is derived from the metamorphism of quartz sandstone. Orthoquartzite and metaquartzite describe different levels of cementation and metamorphism in quartzite. The distinction between orthoquartzite and quartz sandstone lies in the cementation level. As metamorphism progresses, quartz grains in quartzite undergo recrystallization, leading to different textures. Safety and Etymology: Quartzite, being a form of silica, poses risks in workplaces due to hazardous silica dust. Activities like cutting, grinding, and polishing quartzite can release respirable crystalline silica. Workers involved in quartzite processing should take precautions to minimize exposure to silica dust. The term ‘quartzite’ originates from the German word ‘Quarzit’.