igneous
Diorite
Phaneritic Intermediate Plutonic Rock
Mohs hardness: 6-7; Color: Salt and pepper (black and white); Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0
- Hardness
- 6-7
- Color
- Salt and pepper (black and white)
- Luster
- Dull to vitreous
Identified More igneous →
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Physical properties
Mohs hardness: 6-7; Color: Salt and pepper (black and white); Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0
Formation & geological history
Formed by the slow cooling of intermediate silicate magma beneath the Earth's surface in volcanic arcs and mountain-building zones (subduction zones).
Uses & applications
Used as a base material in construction of roads, buildings, and parking lots; historically used for sculpture and decorative stonework due to its durability.
Geological facts
The Code of Hammurabi was inscribed on a black diorite stele; it is often referred to as 'salt and pepper' rock due to the contrast between plagioclase and hornblende.
Field identification & locations
Identify by its coarse grain size and equal distribution of light (plagioclase) and dark (hornblende/biotite) minerals; lack of visible quartz distinguishes it from granite.
