igneous
Diorite
Diorite
Hardness: 6-7 on Mohs scale. Color: Mottled black and white ('salt and pepper' appearance). Luster: Dull to sub-vitreous. Crystal Structure: Phaneritic (coarse-grained coarse crystalline). Cleavage: Visible in individual feldspar and amphibole grains. Specific Gravity: 2.8 - 3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled black and white ('salt and pepper' appearance)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled black and white ('salt and pepper' appearance). Luster: Dull to sub-vitreous. Crystal Structure: Phaneritic (coarse-grained coarse crystalline). Cleavage: Visible in individual feldspar and amphibole grains. Specific Gravity: 2.8 - 3.0.
Formation & geological history
Formed by the slow cooling of intermediate magma beneath the Earth's surface (intrusive). Commonly found in volcanic arcs, mountain building zones (orogens), and large roots of mountains.
Uses & applications
Used primarily as a crushed stone for construction, road base, and drainage. High-quality specimens can be polished for architectural use as countertops, steps, or facing stones, and historically used for sculpture.
Geological facts
The Code of Hammurabi, one of the oldest deciphered writings of significant length in the world, was inscribed on a 7-foot-tall black diorite stele around 1750 BCE.
Field identification & locations
Identify in the field by its characteristic coarse-grained, intermediate 'salt and pepper' look with approximately equal amounts of light plagioclase feldspar and dark minerals like hornblende or biotite. It lacks the significant quartz content found in granite.
