Diorite stone: description and properties

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Diorite stone: description and properties
Diorite stone: description and properties

Diorite stone is an intrusive rock whose composition is intermediate between gabbro and granite. It is formed in volcanic arcs and in mountain structures, where it occurs in large quantities in the form of batholiths in the root parts of island arcs (for example, in Scotland, Norway). Because this stone has a mottled black and white hue, it is often referred to as "s alt and pepper". Diorite is the plutonic equivalent of andesite.

diorite stone

What is diorite?

Diorite is the name of a group of coarse-grained igneous rocks that consist of granite and bas alt. The rock often forms over a convergent plate boundary where the oceanic subsides below the continental.

Partial melting of the oceanic plate leads to the formation of bas altic magma, which rises and penetrates into the granitic rocks of the continental plate. There, bas altic magma mixes with granitic or melts granitic rocks, rising along the continental plate. Thusa melt is obtained, which is intermediate in composition between bas alt and granite. Diorite is formed when such a melt crystallizes below the surface.


Diorite stone is usually composed of sodium-rich plagioclase with less hornblende and biotite. It usually contains little quartz. This makes diorite a coarse-grained rock with a contrasting blend of black and white mineral grains.

diorite stone properties

Diorites are composed primarily of feldspar, plagioclase, amphiboles and micas, with occasional small amounts of orthoclase, quartz or pyroxene.

The chemical composition of the stone is intermediate between that of gabbro and felsite granite.

Historical use

Diorite is an extremely heavy stone that is so difficult to work with that ancient civilizations (such as ancient Egypt) used balls of it to work granite. Its hardness, however, makes it possible to work and polish diorite well, and also ensures the durability of products made from it.

One of the relatively common uses of diorite is for inscriptions. Perhaps the best-known work in existence is Hammurabi's code of laws. It is carved on a stele measuring 2.23 m from black diorite. The original of this work can be seen today in the Louvre in Paris. The use of diorite in art was very important in early Middle Eastern civilizations such as Ancient Egypt, Babylon, Assyria and Sumer. The stone was so valuable that the first great Mesopotamian empire (Akkadian Empire)considered its capture as the goal of military expeditions.

law code of Hammurabi

Physical properties of diorite

The physical properties of rocks are used to determine their type and learn more about them. There are various physical properties of diorite such as hardness, grain size, wear resistance, porosity, luster, strength that define it. The physical properties of diorite rock are vital to determining its structure and use.

Hardness and strength

The physical properties of diorite stone depend on its formation. The physical properties of rocks play an important role in determining its application in various fields. Stones are rated on the Mohs hardness scale, which rates them from 1 to 10. Stones with a hardness of 1-3 are soft rocks, 3-6 are medium hard rocks, and 6-10 are hard rocks. The hardness of diorite is 6-7, while its compressive strength is 225.00 N/mm2. Diorite is not only hard, but also viscous, which determines its high wear resistance. The brilliance of diorite is the interaction of light with its surface. Diorite is a shiny stone. Splitting it is not available. The specific gravity of diorite is 2.8-3. It is inherently opaque and has an impact strength of 2.1.

diorite product

Diorite and andesite

These are similar breeds. They have the same mineral composition and are found in the same geographical areas. The differences are in grain size and cooling rate. Diorite slowly crystallized insideEarth. This slow cooling results in a coarse grain size. Andesite is formed when magma crystallizes rapidly on the Earth's surface. This rapid cooling provides rock with small crystals.

The bottom photo of a diorite stone shows a specimen as it might appear on a polished worktop, facing stone or floor tile. It is typically sold as "white granite" in a carpentry shop or building supply store.

polished diorite

Diorite and granodiorite

Granodiorites, medium to coarse grained rocks are some of the most significant intrusive igneous rocks. It is composed of quartz and differs from granite in that it contains additional plagioclase feldspar. Its other mineral components include hornblende, biotite and augite. Plagioclase (andesine) is usually a double crystal, sometimes completely enclosed in orthoclase. According to the method of formation and appearance, physical appearance, mineral composition and texture, granodiorite is in many ways similar to granite. It is darker in color due to the higher content of plagioclase.


In areas where diorite occurs near the surface, it is sometimes mined for use as rubble. It has a strength that compares favorably with that of granite. It is used as a base material in the construction of roads, buildings and parking lots; used as a drainage stone and for erosion control.

In the stone industry, diorite is often cut intofacing stone, tiles. Ashtrays, blocks, paving stones, curbs and various stone products are made from it. Diorite stone is sold as "granite". The natural stone industry uses the name "granite" for any rock with visible, intertwined feldspar grains. This makes it easier to discuss with clients who don't know how to identify igneous and metamorphic rocks.

bowl of diorite

Diorite in art

Diorite stone is difficult to use in sculpture due to its hardness, variable composition and coarse grain size. For these reasons, it is not a favorite stone of sculptors, although it was popular among the ancients of the profession in the Middle East.

Diorite has the ability to absorb lacquer and is sometimes cut into cabochons or used as a gemstone. In Australia, diorite with beautiful pink feldspar inclusions was cut into cabochons and named "pink marshmallow".


Diorite deposits are relatively rare. Deposits of this rock are scattered all over the world. They are found in countries such as the UK (Aberdeenshire and Leicestershire), Germany (Saxony and Thuringia), Romania, Italy (Sondrio, Guernsey), New Zealand (Coromandel Peninsula, Stewart Island, Fiordland), Turkey, Finland, central Sweden, Egypt, Chile and Peru, as well as in US states such as Nevada, Utah and Minnesota. In Corsica, a Mediterranean island belonging to France, an orbicular (spheroidal) variety of diorite was found, which is mentionedas "Corsite" or "Napoleonite" after their place of origin and the French leader respectively.

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