igneous

Diorite

Intrusive Igneous Diorite (intermediate composition)

Hardness: 6-7 Mohs; Color: Salt-and-pepper (mottled black and white); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.8 - 3.0

Hardness: 6-7 Mohs
Color: Salt-and-pepper (mottled black and white)
Luster: Subvitreous to dull

Identified March 13, 2026More igneous →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6-7 Mohs; Color: Salt-and-pepper (mottled black and white); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.8 - 3.0

Formation & geological history

Formed from the slow cooling of silicate magma beneath the Earth's surface in volcanic arches or subduction zones. Can range in age from the Precambrian to more recent Cenozoic formations.

Uses & applications

Commonly used as a base material in construction of roads and buildings. High-quality specimens are used in architectural stone, flooring, and cemetery markers. Historically used for making tools due to its toughness.

Geological facts

Diorite was used in ancient Egypt and Mesopotamia for sculptures because of its extreme hardness; the Code of Hammurabi was famously inscribed on a pillar of black diorite.

Field identification & locations

Identify in the field by its distinctive 'dalmatian' salt-and-pepper appearance and coarse grain size without visible quartz. It is commonly found in large plutons and is associated with mountain ranges like the Andes or the Alps.

Other igneous specimens

See all

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral