igneous
Diorite
Diorite
Hardness: 6-7 on Mohs scale. Color: Salt and pepper (mottled grey, white, and black). Luster: Phaneritic (visible crystals), dull to vitreous. Crystal structure: Medium to coarse-grained. Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (mottled grey, white, and black)
- Luster
- Phaneritic (visible crystals), dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt and pepper (mottled grey, white, and black). Luster: Phaneritic (visible crystals), dull to vitreous. Crystal structure: Medium to coarse-grained. Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the slow cooling of magma beneath the Earth's surface in volcanic arches and mountain-building zones (subduction zones). Likely Mesozoic to Cenozoic era.
Uses & applications
Used in construction as crushed stone, for cemetery markers, floor tiles, and as 'black granite' in high-end countertops. Highly valued in ancient civilizations for sculpture due to its extreme hardness.
Geological facts
Diorite was used in ancient Egypt for carving hard stones. The Code of Hammurabi was inscribed on a massive basalt/diorite stele. It is often confused with Granite or Gabbro.
Field identification & locations
Identify by its 'salt and pepper' appearance with equal-sized light and dark mineral grains. Found in volcanic mountain ranges like the Andes or Cascades. Very common in glacial till and riverbeds.
