igneous
Diorite
Diorite
Hardness: 6-7 Mohs; Color: Salt-and-pepper (mottled black and white); Luster: Subvitreous 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
- Subvitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (mottled black and white); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8 - 3.0
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface (intrusive). Usually occurs in volcanic arcs or as batholiths in cordilleran mountain ranges. Compositionally intermediate between granite and gabbro.
Uses & applications
Used primarily as a construction material (crushed stone) for road bases and concrete. When polished, it is used for countertops, floor tiles, and as a dimension stone for architectural facings. Historically used in sculpting.
Geological facts
One of the most famous historical uses of diorite was for the Code of Hammurabi, an ancient Babylonian law code inscribed on a large diorite stele over 7 feet tall.
Field identification & locations
Identify in the field by its distinctive 'salt-and-pepper' appearance. Unlike granite, it contains little to no visible quartz. It is found in large intrusive bodies like the Andes Mountains or along the Western coast of North America.
