igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (mottled black and white); Luster: Phaneritic (crystalline); Texture: Coarse-grained; Specific Gravity: 2.8-3.0
- Hardness
- 6-7 (Mohs scale)
- Color
- Salt and pepper (mottled black and white)
- Luster
- Phaneritic (crystalline)
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Salt and pepper (mottled black and white); Luster: Phaneritic (crystalline); Texture: Coarse-grained; Specific Gravity: 2.8-3.0
Formation & geological history
Forms from the slow cooling of magma beneath the Earth's surface in volcanic arcs and at subduction zones. It has a chemical composition intermediate between granite and gabbro.
Uses & applications
Primarily used as a crushed stone for construction, road base, and drainage. Polished varieties are used for floor tiles, countertops, and facing stone in architecture.
Geological facts
The famous Code of Hammurabi was inscribed on a 7-foot tall diorite stele. It is exceptionally durable, making it difficult to carve but long-lasting for ancient monuments.
Field identification & locations
Look for a coarse-grained texture with roughly equal parts dark (hornblende/biotite) and light (plagioclase feldspar) minerals. Common in mountainous regions near plate boundaries like the Andes.
