igneous

Diorite

Diorite (an intrusive igneous rock)

Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper appearance (mix of black and white/gray). Luster: Phaneritic (visible crystals), dull to vitreous. Crystal structure: Medium to coarse-grained. Specific gravity: 2.8-3.0.

Hardness: 6-7 on Mohs scale
Color: Salt-and-pepper appearance (mix of black and white/gray)
Luster: Phaneritic (visible crystals), dull to vitreous

Identified May 4, 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 arcs and at subduction zones. It often happens in continental crust above a subducting oceanic plate.

Uses & applications

Used primarily as crushed stone for construction and base material for roads. High-quality specimens are polished for use as 'black granite' in countertops, tiles, and monuments.

Geological facts

Diorite was used by the Ancient Egyptians and Mesopotamians for sculpture because of its extreme hardness; the famous Code of Hammurabi is inscribed on a diorite stele.

Field identification & locations

Identified by its distinctive speckled appearance with roughly equal parts light and dark minerals. Look for it in mountain ranges and near larger granitic batholiths. It lacks the pinkish potassium feldspar found in granite.

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