igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 on Mohs scale. Color: Salt and pepper (mottled black and white). Luster: Phaneritic (medium to coarse-grained crystals). Structure: Granular/Crystalline. Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (mottled black and white)
- Luster
- Phaneritic (medium to coarse-grained crystals)
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt and pepper (mottled black and white). Luster: Phaneritic (medium to coarse-grained crystals). Structure: Granular/Crystalline. Specific gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of intermediate magma beneath the Earth's surface in volcanic arcs and mountain-building zones (subduction zones). Usually ages from Precambrian to Cenozoic.
Uses & applications
Used in construction as a base material (crushed stone), for architectural facings, floor tiles, and historically for stone carvings/sculpture (it is extremely durable).
Geological facts
Diorite was used in ancient Egypt and Mesopotamia to carve hard-wearing inscriptions. The famous Code of Hammurabi was inscribed on a massive stele of black diorite.
Field identification & locations
Identify by its 'salt and pepper' appearance without visible quartz. Found in roots of mountains or exposed batholiths. Collectors look for even distribution of plagioclase fieldspar (white) and amphibole/biotite (black).
