igneous
Diorite
Diorite (intermediate plutonic rock)
Phaneritic (coarse-grained) texture with a 'salt and pepper' appearance. Hardness: 6-7 on Mohs scale. Color: Black and white. Luster: Dull to sub-vitreous. Structure: Massive, crystalline. Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Black and white
- Luster
- Dull to sub-vitreous
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Physical properties
Phaneritic (coarse-grained) texture with a 'salt and pepper' appearance. Hardness: 6-7 on Mohs scale. Color: Black and white. Luster: Dull to sub-vitreous. Structure: Massive, crystalline. Specific gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of intermediate-composition magma deep beneath the Earth's surface (plutonic). It is typically found in volcanic arcs and mountain-building regions above subduction zones.
Uses & applications
Used as a base material in construction (crushed stone), for paving, building facades, and historically for statues and monuments due to its hardness and durability.
Geological facts
The famous Code of Hammurabi was inscribed on a massive black diorite stele. In ancient Egypt, diorite was highly valued for its extreme hardness, making it ideal for permanent inscriptions and hard-stone sculptures.
Field identification & locations
Identify by looking for a coarse-grained igneous rock that lacks visible quartz (unlike granite) and has roughly equal amounts of light plagioclase feldspar and dark minerals like hornblende or biotite. It is found in large batholiths in many mountain ranges.
