igneous
Diorite
Intermediate Phaneritic Igneous Rock
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (mottled black and white); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained coarse crystals visible to the eye); Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' (mottled black and white)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (mottled black and white); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained coarse crystals visible to the eye); Specific gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of intermediate silicate magma beneath the Earth's surface in volcanic arcs and mountain-building zones (subduction zones). Often associated with batholiths and laccoliths.
Uses & applications
Used primarily as crushed stone for road construction and base material. In higher grades, it is used as dimension stone for building facades, floor tiles, and occasionally as a base for cemetery monuments.
Geological facts
Diorite was used in ancient Egypt for sculpting because of its extreme hardness; the famous Code of Hammurabi was inscribed on a polished diorite stele. It is often confused with granite but lacks the significant quartz content found in granite.
Field identification & locations
Identify in the field by its distinctive black-and-white speckled appearance and checking for a Lack of visible quartz. Commonly found in the roots of mountain ranges like the Andes or the Cascades.
