igneous
Diorite
Diorite
Hardness (Mohs scale): 6-7. Color: Salt and pepper (mottled black and white). Luster: Phaneritic (coarse-grained, crystalline). Crystal structure: Massive, equigranular. Specific gravity: 2.8-3.0.
- Color
- Salt and pepper (mottled black and white)
- Luster
- Phaneritic (coarse-grained, crystalline)
Identified More igneous →
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Physical properties
Hardness (Mohs scale): 6-7. Color: Salt and pepper (mottled black and white). Luster: Phaneritic (coarse-grained, crystalline). Crystal structure: Massive, equigranular. Specific gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of silicate magma below Earth's surface (intrusive). Usually found in volcanic arcs and mountain building zones above subduction zones.
Uses & applications
Used as a base material in construction (crushed stone), road building, and occasionally as a dimensional stone for floor tiles or building facades. Historically used for sculpture (e.g., Code of Hammurabi).
Geological facts
Diorite is often called black granite by the construction industry, though geologically it lacks enough quartz to be a true granite. One of the most famous diorite artifacts is the Code of Hammurabi stele.
Field identification & locations
Identified by its phaneritic texture and lack of visible quartz (less than 5% quartz). Found in large plutons. Look for the distinct speckled look where white plagioclase feldspar meets dark hornblende or biotite.
