igneous
Diorite
Diorite
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (black and white/gray); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.8 to 3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' (black and white/gray)
- Luster
- Subvitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (black and white/gray); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific Gravity: 2.8 to 3.0.
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface in volcanic arches or mountain-building zones (subduction zones). It is a plutonic rock often associated with granitic or gabbroic intrusions.
Uses & applications
Commonly used as a base material in construction, crushed stone for roads, and occasionally as a facing stone for buildings or monuments. Some varieties are used in lapidary work.
Geological facts
Diorite is often called 'salt and pepper rock' because of its distinct mottled appearance. In ancient Egypt and Mesopotamia, it was prized for its extreme hardness and used for sculpting statues and law codes, such as the Code of Hammurabi.
Field identification & locations
Identified by its medium-to-coarse grain size and roughly equal balance of light and dark minerals. Look for it in mountainous regions or along riverbeds where erosion has transported plutonic rocks.
