How is the structure of a quartzite



  Quartzite is a fine to medium-grained metamorphic rock.

Appearance and properties

In most cases, quartzite is white-gray in color. Due to impurities from magnetite and pyrite it is sometimes colored brown or gray. Outwardly it bears a certain resemblance to marble, even if the mineral composition is completely different.

Quartzite, which consists almost exclusively of interconnected, recrystallized quartz grains, is a very hard, brittle rock that is resistant to erosion and weathering.

A rare variety of quartzite is the flexible itakolumite or (due to its high content of sheet silicates) Articulated quartz.

Emergence

Quartzite is formed by metamorphosis from sandstone. The individual quartz grains are deformed by a combination of high pressure and high temperature as well as mechanical stress. When they recrystallize, they then grow beyond their original grain boundaries (see picture) and form a densely networked structure. Structures formerly contained in the sandstone, such as fossils, are mostly destroyed by this process, but in individual cases they can be retained in outline.

The different variants of quartzite arise from the different mineral compositions of the original sandstones.

Occurrence

 

Quartzite is widespread worldwide and is a fairly common rock in metamorphic orogenous complexes. In Germany, quartzite can be found in the Taunus and Hunsrück regions, on both sides of the Middle Rhine Valley (for example at the gold mine). Further occurrences are in the Eifel and in the Westerwald. It is also found in the western Harz; there the quartzite is slightly reddish in color and is called Quarry mountain quartzite designated. Quartzites are also occasionally found as glacial debris in northern Germany.

Economical meaning

Due to its hardness and resistance, quartzite is used in a variety of ways in the natural stone industry. Above all, it is processed into chippings or paving stones or used in a very pure form as a raw material for quartz. Quartzites are among the hardest rocks of all. They are processed exclusively with machines, because they are too hard for manual processing. That is why they are called machine stones in the stone trade. They are particularly suitable in areas that are heavily used and subject to heavy wear. They are particularly suitable for floor and stair coverings as well as for kitchen worktops, but they are also used regionally for gardens.

Most quartzites are imported, whereby the blue quartzite Azul do Macaubas from Brazil is extremely popular because it has a daily price like gold. In the Taunus, this rock is mined in a quartzite plant in the Köpperner valley.

Types of natural stone

  • Azul Imperial (Brazil, Bahia)
  • Azul de Macaubas (Brazil, Bahia)
  • Alta quartzite (Norway, Alta)

See also:List of rocks.

Category: Metamorphite