Igneous

Diorite

Intermediate plutonic igneous rock

Hardness: 6-7 (Mohs scale); Color: Salt-and-pepper (speckled black and white/gray); Luster: Sub-vitreous to dull; Crystal structure: Phaneritic (coarse-grained coarse crystals visible to the naked eye); Cleavage: Distinct in feldspar minerals; Specific gravity: 2.8 - 3.0.

Hardness: 6-7 (Mohs scale)
Color: Salt-and-pepper (speckled black and white/gray)
Luster: Sub-vitreous to dull

Identified March 8, 2026More igneous →

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Physical properties

Formation & geological history

Formed by the slow cooling of magma beneath the Earth's surface in volcanic arcs and above subduction zones. Typically formed during the Phanerozoic eon, often associated with continental margins.

Uses & applications

Used primarily as a decorative stone in architecture, as a base material in construction (crushed stone), for grave markers, and historically for sculptures and tools due to its extreme hardness.

Geological facts

Diorite was used by ancient civilizations like the Egyptians and Akkadians for monumental sculpture. The famous Code of Hammurabi was inscribed on a massive black diorite stele.

Field identification & locations

Identify in the field by its phaneritic texture and 'salt and pepper' appearance caused by roughly equal amounts of light plagioclase feldspar and dark minerals like hornblende or biotite. Commonly found in batholiths and mountain ranges like the Andes.

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