igneous
Diorite
Intermediate Phaneritic Igneous Rock
Hardness: 6-7 Mohs; Color: Salt and pepper (mottled black and white); Luster: Sub-vitreous 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
- Sub-vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (mottled black and white); Luster: Sub-vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0
Formation & geological history
Formed by the slow cooling of magma below the Earth's surface (intrusive) in subduction zones and mountain-building regions. Often associated with volcanic arcs and tectonic margins.
Uses & applications
Used as a base material in road construction, as crushed stone, and for building facades or floor tiles. Historically used for sculpture and durable stone tools.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for sculptures and inscriptions, including the famous Code of Hammurabi, due to its extreme durability and hardness.
Field identification & locations
Field identification is based on its coarse grain size and roughly equal balance of light plagioclase feldspar and dark minerals like hornblende or biotite. It is often found in large batholiths or as glacial erratics.
