igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white plagioclase feldspar and black minerals); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.
- Hardness
- 6-7 Mohs
- Luster
- Subvitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white plagioclase feldspar and black minerals); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the slow cooling of magma deep beneath the Earth's surface, typically above subduction zones at convergent plate boundaries. Most specimens range from Proterozoic to Cenozoic in age.
Uses & applications
Used in construction as crushed stone, as a base material for roads, and occasionally as a decorative building stone or for countertops. Historically used for carving by ancient civilizations.
Geological facts
The Code of Hammurabi, one of the oldest deciphered writings of significant length in the world, was inscribed on an 8-foot-tall diorite stele.
Field identification & locations
Identify in the field by its phaneritic texture and its 'salt-and-pepper' appearance, containing roughly equal amounts of light and dark minerals. Common in volcanic arc settings like the Andes Mountains.
