igneous
Diorite
Diorite (intermediate intrusive igneous rock)
Porphyritic or phaneritic texture with 'salt and pepper' appearance. Hardness: 6-7 (Mohs scale), Color: black and white/gray, Luster: dull to vitreous, Specific Gravity: 2.8-3.0.
- Luster
- dull to vitreous, Specific Gravity: 2
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Physical properties
Porphyritic or phaneritic texture with 'salt and pepper' appearance. Hardness: 6-7 (Mohs scale), Color: black and white/gray, Luster: dull to vitreous, Specific Gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of magma below the Earth's surface in volcanic arcs and mountain-building zones (subduction zones). Primarily composed of plagioclase feldspar and hornblende.
Uses & applications
Historically used for sculpture (like the Code of Hammurabi) due to its extreme hardness; currently used as crushed stone for roads or as polished 'black granite' for countertops.
Geological facts
The Code of Hammurabi was inscribed on a 7-foot tall stele of black diorite. It is often confused with granite but lacks significant quartz content.
Field identification & locations
Identify by the nearly equal mix of light and dark minerals with visible crystals. Found in mountain ranges like the Andes or the Alps. Look for a speckled, non-banded appearance.
