igneous
Diorite
Diorite (Intermediate intrusive 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). 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). Specific gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of intermediate-composition magma beneath the Earth's surface (plutonic). It often occurs in volcanic arcs and mountain building zones above subduction zones.
Uses & applications
Used in construction as crushed stone or 'black granite' for countertops, floor tiles, and building veneers. Historically used for carving sculptures and steles.
Geological facts
The Code of Hammurabi, one of the oldest deciphered writings of significant length in the world, was inscribed onto a seven-foot-tall black diorite stele around 1754 BCE.
Field identification & locations
Identify by its coarse-grained 'salt and pepper' appearance; it lacks the visible quartz typical of granite. Commonly found in large mountain ranges such as the Andes, Alps, and Cascades.
