igneous

Diorite (with Quartz veins)

Diorite

Hardness: 6-7 (Mohs scale); Color: Black and white 'salt and pepper' appearance; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.

Hardness: 6-7 (Mohs scale)
Color: Black and white 'salt and pepper' appearance
Luster: Vitreous to dull

Identified April 3, 2026More igneous →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Black and white 'salt and pepper' appearance; Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.

Formation & geological history

Formed through the slow cooling of magma beneath the Earth's surface (intrusive). Usually found in volcanic arcs and mountain-building regions associated with subduction zones.

Uses & applications

Used primarily as crushed stone for road construction, drainage, and foundation fill. High-quality specimens are polished for use as dimension stone, countertops, and floor tiles.

Geological facts

Diorite was used by ancient civilizations, such as the Egyptians and Sumerians, for making statues and stelae because of its extreme hardness; the Code of Hammurabi was famously inscribed on a diorite stele.

Field identification & locations

Identify in the field by its distinctive 'salt and pepper' look, consisting of white plagioclase feldspar and dark hornblende/biotite. It is found in large mountain ranges such as the Andes or the Cascades.

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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