igneous
Diorite
Intrusive Igneous Diorite (intermediate composition)
Hardness: 6-7 Mohs; Color: Salt-and-pepper (mottled black and white); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.8 - 3.0
- Hardness
- 6-7 Mohs
- Color
- Salt-and-pepper (mottled black and white)
- Luster
- Subvitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (mottled black and white); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the slow cooling of silicate magma beneath the Earth's surface in volcanic arches or subduction zones. Can range in age from the Precambrian to more recent Cenozoic formations.
Uses & applications
Commonly used as a base material in construction of roads and buildings. High-quality specimens are used in architectural stone, flooring, and cemetery markers. Historically used for making tools due to its toughness.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for sculptures because of its extreme hardness; the Code of Hammurabi was famously inscribed on a pillar of black diorite.
Field identification & locations
Identify in the field by its distinctive 'dalmatian' salt-and-pepper appearance and coarse grain size without visible quartz. It is commonly found in large plutons and is associated with mountain ranges like the Andes or the Alps.
