What is granite


Author: Torsten Purle (steine-und-minerale.de) | Last update: 29.03.2021

Granite - properties, formation and use

english: granite | French: granite

Granite - granular stone; This is the translation of the name, which comes from Latin, whereby the name granite is based on the appearance of the rock, which consists of velen mineral grains.

Properties of granite

Definition: Granite is igneous rock with intrusive origin (so-called plutonite) and acidic chemistry.

The color of granite appears light in its entirety, but on closer inspection it is varied and of pink, white-gray, greenish, yellowish, dark-gray or blue-white color.
The light rock color is mainly due to the orthoclase feldspars present in the rock (proportion 35 to 90%), which are the main mixture (in terms of quantity, the mineral that dominates the rock) alongside quartz (proportion between 20 to 60%), microcline, plagioclase feldspar Muscovite, biotite, amphibolite and augite predominate.

If you take a closer look at granite, you can see that the light mineral components in pink, salmon and white in the granite represent feldspars. The dark mica mineral biotite appears as dark gray to black crystals, while the light mica muscovite produces a white-silver shimmering color, and quartz appears gray, contrary to the actual light color. The reason for this is that quartz, due to its transparent to translucent transparency, acts as a "window" in the rock and gives the impression of gray-shaded mineral areas.

Some of the feldspar crystals in granites can reach a size of up to 10 cm.
Ultimately, it is important and decisive for the definition of granite that Orthoclase feldspar predominates over plagioclase feldspar, otherwise it is granodiorite.

Hornblende, garnet, andalusite, sillimanite and cordierite, among others, occur in granite as secondary parts (= minerals in the rock with a proportion of up to 5%).

The even smaller amounts of the accessories in granite are represented by apatite, zircon, topaz, beryl, tourmaline, titanite, magnetite, rutile, hematite, pyrite, monazite and fluorite.

Inky blue, circular inclusions of azurite in K2 azurite or K2 granite are particularly rare.

Depending on the fine color differences or particularly prominent mineral content, a distinction is made between the following types of granite:

  • pink granite
  • white granite
  • porphyry granite
  • graphic granite
  • Hornblende granite

The structure of granite is very compact and massive. The xeno- and idiomorphic crystals are stored irregularly. The grain size is medium to coarse.
The density of the rock of intrusive origin is 2.6 to 2.7 g / cm3.

Distribution and formation of granite

Granite is a plutonite - a rock that is formed by slow cooling and solidification of magma in the earth's crust, i.e. below the earth's surface.

The crystallization of the aggregates or minerals from which granite is made up is caused by the mineral's own melting points. Biotite and other dark minerals are the first products of crystallization, followed by quartz and feldspars.
Thick, overlying layers of rock initially prevent the molten rock from penetrating the surface of the earth, so that the molten rock is "forced" to solidify below the surface of the earth. Huge batholiths are witnesses of how the granitoid rock mass found its way into the upper crust of the earth in tectonic faults. Due to the high temperatures of the rock melt, it is not uncommon for the surrounding rock to be integrated into the granite mass as xenolite without being melted.
The granite complexes only come to light in the course of weathering or other erosion of the surface. The Brocken (1142 m above sea level) in the Harz Mountains is an example of such granite complexes.

Granite is a common rock. 44% of all continental rocks are granites.
Finland is known as the sites; Sweden: Norway; Black Forest, Odenwald, Thuringian Forest, Ore Mountains, Harz, Fichtel Mountains, Bavarian Forest / Germany; Alps; Bohemia / Czech Republic; Vosges, Brittany / France: Canada; Rocky Mountains, Appalachian Mountains / USA; Himalayas and Urals / Russia.

Importance and use of granite

The high weather resistance of granite is one reason for the many uses of granite natural stone, e.g. as a curb, curb and paving stone. In interior design, granite is used as a floor covering, worktop or for facade cladding. In art, granite is a sought-after sculptural material.

A comparatively unknown use of granite is whiskey stones, which are used in place of ice to cool whiskey without affecting the taste or watering down the drink.

See also:
⇒ Font granite
⇒ Differentiate between granite and gneiss
⇒ Black granite

⇒ Bauer, J .; Tvrz, F. (1993): The Cosmos Mineral Guide. Minerals rocks precious stones. An identification book with 576 color photos. Gondrom Verlag GmbH Bindlach
⇒ Pellant, C. (1994): Stones and Minerals. Ravensburger nature guide. Ravensburger Buchverlag Otto Maier GmbH
⇒ Schumann, W. (1991): Minerals rocks - characteristics, occurrence and use. FSVO nature guide. BLV Verlagsgesellschaft mbH Munich
⇒ Maresch, W., Medenbach, O .; Trochim, H.-D. (1987): The colored natural guide rocks. Mosaik Verlag GmbH Munich
⇒ Murawski, H. (1992): Geological Dictionary. Ferdinand Enke Verlag Stuttgart
⇒ Schumann, W. (1994): Collecting stones and minerals; find, prepare, determine. BLV Verlag Munich

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