igneous

Diorite

Diorite (Intermediate intrusive igneous rock)

Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (mottled black and white); Luster: Phaneritic (crystalline/dull to vitreous); Crystal Structure: Coarse-grained intrusive; Cleavage: Good in two directions (due to feldspar and amphibole); Specific Gravity: 2.8 - 3.0

Hardness: 6-7 on Mohs scale
Color: 'Salt and pepper' (mottled black and white)
Luster: Phaneritic (crystalline/dull to vitreous)

Identified March 23, 2026More igneous →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed by the slow cooling of magma beneath the Earth's surface in volcanic arches and subduction zones. It has a chemical composition intermediate between granite and gabbro. Most specimens range from Precambrian to Cenozoic in age.

Uses & applications

Used in construction as crushed stone or road base. It is also polished for use as dimension stone for countertops, floor tiles, and building veneers. In ancient times, it was used by Egyptians and Sumerians for monumental sculpture due to its extreme hardness.

Geological facts

Diorite was used by the ancient Mesopotamians to carve the famous 'Code of Hammurabi' (stela), now in the Louvre. Its durability is so high that it is often difficult to carve without modern tools.

Field identification & locations

Identify in the field by its distinctive black-and-white 'dalmatian' appearance. It contains mostly white plagioclase feldspar and dark minerals like hornblende or biotite. It lacks the pinkish potassium feldspar and high quartz content found in granite. Found commonly in the Andes Mountains, Italy, and the UK.

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