igneous
Diorite
Intermediate Phaneritic Igneous Rock
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (mottled black and white/gray); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (mottled black and white/gray)
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (mottled black and white/gray); Luster: Vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0
Formation & geological history
Formed by the slow cooling of magma deep beneath the Earth's surface (intrusive). It is intermediate in composition between granite and gabbro, typically found in volcanic arcs and mountain building zones.
Uses & applications
Used as a base material in construction, crushed stone for roads, and occasionally as a decorative building stone or for monuments due to its durability.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for sculptures and tablets because of its extreme hardness; the Code of Hammurabi was inscribed on a diorite stele.
Field identification & locations
Identify by the coarse salt-and-pepper grain distribution. It lacks the pinkish potassium feldspar of granite and the heavy dark minerals of gabbro. Found in large plutons or sills.
