igneous

Diorite

Diorite (Intermediate intrusive igneous rock)

Hardness: 6-7 (Mohs scale); Color: 'Salt and pepper' (mottled black/dark green and white/grey); Luster: Sub-vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.

Hardness: 6-7 (Mohs scale)
Color: 'Salt and pepper' (mottled black/dark green and white/grey)
Luster: Sub-vitreous to dull

Identified April 10, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow cooling of intermediate-composition magma deep beneath the Earth's surface in volcanic arches or subduction zones. It represents a composition between granite and gabbro.

Uses & applications

Primarily used as a base material in construction (crushed stone), for paving, and occasionally as a facing stone for buildings or ornamental monuments due to its ability to take a high polish.

Geological facts

Ancient Egyptians used diorite to carve extremely hard sculptures, such as the famous statue of Khafre and the Code of Hammurabi, because of its durability and fine grain.

Field identification & locations

Identify in the field by looking for a coarse-grained texture where dark minerals (hornblende/biotite) and light minerals (plagioclase feldspar) are present in roughly equal amounts, usually lack visible quartz.

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