igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 Mohs; Color: Salt and pepper (black and white/gray); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper (black and white/gray)
- Luster
- Subvitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (black and white/gray); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of silicate magma underground in the Earth's crust, typically in volcanic arcs or above subduction zones. Usually Proterozoic to Cenozoic in age.
Uses & applications
Used primarily as road base, construction aggregate, and dimension stone for building facades and memorials. Polished varieties are used for countertops and floor tiles.
Geological facts
Diorite was used by ancient civilizations like the Egyptians and Sumerians for statues and tools because of its extreme hardness. The famous Code of Hammurabi was inscribed on a diorite stele.
Field identification & locations
Identify by its 'salt and pepper' look with equal parts light and dark minerals; unlike granite, it contains little to no visible quartz. Found in massive batholiths and mountain ranges like the Andes.
