igneous
Diorite
Diorite (plutonic igneous rock)
Hardness: 6-7 (Mohs); Color: Salt and pepper (mottled grey, white, black); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.
- Hardness
- 6-7 (Mohs)
- Color
- Salt and pepper (mottled grey, white, black)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 (Mohs); Color: Salt and pepper (mottled grey, white, black); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.
Formation & geological history
Formed through the slow cooling of silicate magma below Earth's surface, typically in volcanic arcs or above subduction zones. Can range from Precambrian to Cenozoic in age.
Uses & applications
Primarily used as a crushed stone for construction, road base, and drainage. High-quality specimens are used as decorative stone, countertops, or for carving (e.g., Code of Hammurabi).
Geological facts
The famous Code of Hammurabi stele was carved into a massive slab of black diorite. It is often called 'salt and pepper' rock due to its mixed light and dark mineral content.
Field identification & locations
Identify in the field by its phaneritic texture and a roughly equal mix of light and dark minerals. Common in continental crust and mountain ranges like the Andes.
