igneous
Diorite (Spotted)
Diorite (Intrusive igneous rock)
Hardness: 6-7 (Mohs scale); Color: Black and white (salt and pepper appearance); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (medium to coarse-grained); Cleavage: Two directions (amphibole/feldspar); Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 (Mohs scale)
- Color
- Black and white (salt and pepper appearance)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Black and white (salt and pepper appearance); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (medium to coarse-grained); Cleavage: Two directions (amphibole/feldspar); Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the slow cooling of silicate magma below the Earth's surface, typically in volcanic arcs or above subduction zones. It represents a composition intermediate between felsic granite and mafic gabbro.
Uses & applications
Commonly used as a base material in construction, for road stone, and occasionally polished for use as dimension stone, tiles, or decorative items.
Geological facts
The famous Code of Hammurabi was inscribed on a seven-foot-tall stele of black diorite. It is often referred to as 'salt and pepper' rock due to its contrasting mineral colors.
Field identification & locations
Identify by its contrasting black-and-white speckled appearance and crystalline texture. It is harder than marble and can be found in mountain ranges such as the Andes or the Alps.
