igneous

Diorite

Phaneritic Intermediate Plutonic Rock (Diorite)

Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (speckled black and white). Luster: Dull to sub-vitreous. Structure: Phaneritic (coarse-grained). Cleavage: Present in feldspar and amphibole minerals. Specific Gravity: 2.8-3.0.

Hardness: 6-7 on Mohs scale
Color: Salt-and-pepper (speckled black and white)
Luster: Dull to sub-vitreous

Identified February 13, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow cooling of magma beneath the Earth's surface (intrusive) in volcanic arcs or above subduction zones. Typically formed during orogenic (mountain-building) events across various geological eras.

Uses & applications

Used primarily as a construction material (crushed stone) for roads and drainage. In polished form, it is used for countertops, floor tiles, and grave markers. Historically used for carving by ancient civilizations.

Geological facts

Ancient Egyptians and Maya civilizations used diorite for statues and stelae because of its extreme hardness. The famous Code of Hammurabi was inscribed on a large diorite stele.

Field identification & locations

Identify in the field by its speckled 'salt and pepper' appearance and lack of visible quartz (unlike granite). Found in areas with mountain-building history like the Andes, the Alps, and the Scottish Highlands.

Other igneous specimens

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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