What kind of rock is diorite


Author: Torsten Purle (steine-und-minerale.de) | Last update: May 20, 2021

Diorite - properties, formation and use

English: diorite | French: diorite

The name diorite, derived from the Greek, indirectly refers to the rock diabase, with which diorite can be confused because of the similarity. Main criterion of Distinction (hence the name, Greek) is the composition, insofar as diorite in contrast to diabase no orthoclase having.

Properties of diorite

definition: Diorite is an igneous rock of intrusive origin with an intermediate composition (i.e. SiO2Content: 52 to 65%).

The rock is from light to dark gray in color, but can also be greenish-gray, blue-gray to almost black be.
Due to its dark color, diorite is also known as black granite in addition to other rocks of a dark color, even if the composition differs from that of "real" granite.

The main mixture parts, i.e. predominantly in terms of quantity, of the polymineral rock are plagioclase feldspar, hornblende, biotite and augite.

In addition to garnet, titanite and apatite, magnetite, zirconium, pyroxene and ilmenite with a proportion of up to five percent in diorite can also be represented as secondary components.

In some cases the magmatite contains olivine, microcline or quartz, in the latter case it is called quartz diorite.

Furthermore, diorite is based on the proportions of dark mixture parts in Leuco and meladiorite differentiated, which have less than 25% (leucodiorite) or more than 50% dark minerals (meladiorite) in the mineral inventory.

The structure of diorite is grainy, the grain size varies between fine to medium-grained. The crystal form of the minerals that form it is both xenomorphic and idiomorphic, which are compactly arranged in the rock compound without any adjustment.
The so-called one is an exception Spherical diorite (orbiculite), in which the batch parts are regulated in a ring-shaped and sorted manner.

The density of diorite is 2.85 to 3.05 g / cm3 and according to the mineralogist Gustav Rose (1798 to 1873) "the hardest rock that miners know".

Origin and distribution of diorite

Diorite emerges as deep rock from the slow cooling and crystallization of magmas that have penetrated into the earth's crust, often also in connection with intrusions of gabbro and granite.

Diorites are found all over the world. Locations of the rock in Germany are among others in Löbau / Oberlausitz / Saxony; Dessau, Harz / Saxony-Anhalt; Ruhla, Kyffhäuser / Thuringia; Odenwald / Hessen; Bavarian Forest, Spessart / Bavaria and Black Forest / Baden-Württemberg. Further occurrences were in Lower Austria (Waldviertel) / Austria; Switzerland; Leicestershire / England; Scotland; Sweden; Finland; Brittany and Normandy / France; Romania; South Tyrol, Piedmont / Italy; Turkey; Egypt; New Zealand; Andes / South America; Arizona, Nevada, Minnesota / USA; China and Japan documented.

Importance and uses of diorite

Diorite has been a sought-after natural stone since ancient times, which was already used in ancient Greece, Rome and also by the Egyptians. Among other things, columns for temples, stairs or art and everyday objects were made from the stone material. In addition, due to its higher hardness, diorite was used as a tool for processing granite.
Nowadays, diorite is particularly important as curb and paving stone as well as gravel, as it is very resistant to weathering.

Also interesting:
⇒ Granodiorite profile
⇒ Black granite
⇒ The difference between lava and magma

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