Quartzite

This is a metamorphic rock, consisting mainly of quartz - one of the most abundant minerals in the earth's crust. Quartzite was formed by metamorphism (structural change under the influence of high temperatures and pressure) from siliceous sediments. Most often, its formation is associated with the recrystallization of quartz sandstones or igneous rocks, such as porphyry.
The stone has a dense granular structure: microscopic grains of quartz merge into a solid mass with a splintered or conchoidal fracture. At a fracture, the stone has a typical quartz luster. According to the classification of M. Bauer, the breed belongs to semiprecious ornamental stones - this order also includes malachite, jasper and jade. Basic shades: white, gray, red. In nature, quartzites are found in other colors: light yellow, brown, blue.

Many varieties of quartzite are valuable minerals. Ferruginous (magnetite) quartzites are the most important iron ore. A special variety is secondary quartzite. Deposits of secondary quartzites are formed as a result of relatively low-temperature metasomatic transformation of acidic and intermediate effusive, less often intrusive acidic rocks and their tuffs. Deposits of gold, copper, molybdenum, polymetals and pyrite are associated with secondary quartzite.
In our country, the most valuable and beautiful variety is crimson Shoksha quartzite; quartzite is mined on the western shore of Lake Onega in Karelia.