igneous

Diorite

Phaneritic Intermediate Plutonic Rock (Diorite)

Hardness: 6-7 (Mohs scale); Color: 'Salt and pepper' (mottled black and white/grey); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Two directions (from feldspar/hornblende content); Specific Gravity: 2.8-3.0

Hardness: 6-7 (Mohs scale)
Color: 'Salt and pepper' (mottled black and white/grey)
Luster: Dull to sub-vitreous

Identified March 24, 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 and above subduction zones. Typically Proterozoic to Cenozoic in age.

Uses & applications

Used in construction as crushed stone or 'black granite' for countertops, floor tiles, and building veneers; historically used for sculpture and monuments (e.g., Code of Hammurabi).

Geological facts

Famous historical artifacts like the Code of Hammurabi stele were carved into diorite due to its immense durability. It is often confused with gabbro or granite but contains less quartz than granite and more plagioclase than gabbro.

Field identification & locations

Identify by its distinct medium-to-coarse 'salt and pepper' texture. Common in mountain roots such as the Andes, Cascades, and the Alps. Look for visible interlocking crystals of white plagioclase and dark hornblende or biotite.

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