igneous
Diorite
Diorite (Intermediate Plutonic Rock)
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' mixture of black and white; Luster: Phaneritic (crystalline); Structure: Massive, coarse-grained; Specific Gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' mixture of black and white
- Luster
- Phaneritic (crystalline)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' mixture of black and white; Luster: Phaneritic (crystalline); Structure: Massive, coarse-grained; Specific Gravity: 2.8-3.0
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface in volcanic arcs and subduction zones. Typically associated with mountain building events and older continental crust.
Uses & applications
Used primarily as crushed stone for road construction and as dimension stone for building facades, floor tiles, and countertops. Occasionally used as a base for carvings.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for monumental sculpture because of its extreme hardness; the Code of Hammurabi was inscribed on a diorite stele.
Field identification & locations
Identify by its coarse 'salt and pepper' appearance with roughly equal parts light (plagioclase) and dark (hornblende/biotite) minerals. Found in large mountain ranges like the Andes or Alps.
