igneous
Diorite
Diorite (Intermediate Plutonic Rock)
Hardness: 6-7 Mohs; Color: Salt and pepper (black and white); Luster: Dull to sub-vitreous; Crystal Structure: Phaneritic (coarse-grained); Specific Gravity: 2.8 - 3.0
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper (black and white)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (black and white); Luster: Dull to sub-vitreous; Crystal Structure: Phaneritic (coarse-grained); Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed by the slow cooling of silicate magma beneath the Earth's surface in volcanic arcs and mountain-building zones (subduction zones). It consists mainly of plagioclase feldspar and hornblende/biotite.
Uses & applications
Used primarily as crushed stone for road construction and as a decorative building stone known as 'black granite'. Historically used for sculptures and inscriptions, such as the Code of Hammurabi.
Geological facts
The famous Code of Hammurabi was inscribed on a 7-foot tall stele of black diorite. It is often confused with granite but lacks significant quartz.
Field identification & locations
Identify by its 'salt and pepper' appearance and lack of visible quartz crystals. Found in locations like the Andes Mountains, Italy, and various parts of North America.
