igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 on Mohs scale. Color: Salt and pepper (mottled black and white). Luster: Dull to sub-vitreous. Crystal Structure: Phaneritic (coarse-grained). Cleavage: Good (in feldspar and amphibole minerals). Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (mottled black and white)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt and pepper (mottled black and white). Luster: Dull to sub-vitreous. Crystal Structure: Phaneritic (coarse-grained). Cleavage: Good (in feldspar and amphibole minerals). Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through the slow cooling of intermediate magma beneath the Earth's surface in volcanic arcs and mountain-building regions (subduction zones). It is found in large mountain ranges such as the Andes.
Uses & applications
Used primarily as a crushed stone for road construction, drainage, and erosion control. Occasionally polished as ornamental stone or used as a durable dimension stone for monuments and floor tiles.
Geological facts
Diorite is often called 'salt and pepper rock' due to its distinct black-and-white speckled appearance. In Ancient Egypt, it was highly prized for its extreme hardness and used to carve statues.
Field identification & locations
Identify by its coarse-grained texture and balanced mix of light (Plagioclase feldspar) and dark (Hornblende/Biotite) minerals. Unlike granite, it lacks significant visible quartz and potassium feldspar.
