igneous
Diorite
Phaneritic intermediate plutonic rock
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (black and white); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' (black and white)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (black and white); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.8-3.0
Formation & geological history
Formed by the slow cooling of intermediate-composition magma beneath the Earth's surface (intrusive plutonic). Often found in mountain building zones above subduction zones.
Uses & applications
Used as crushed stone for road construction, base material for driveways, and occasionally as dimension stone for building facades or floor tiles.
Geological facts
Diorite is often mistaken for granite, but contains little to no quartz. It was used by ancient civilizations, such as the Egyptians and Sumerians, to carve hard-wearing statues and tablets like the Code of Hammurabi.
Field identification & locations
Identified by its balanced 'salt and pepper' appearance caused by nearly equal amounts of light plagioclase feldspar and dark minerals like hornblende or biotite. Unlike granite, it lacks visible pink or white quartz crystals.
