igneous
Diorite
Intermediate intrusive igneous rock
Hardness: 6-7 on Mohs scale; Color: Salt and pepper appearance (black and white speckled); Luster: Vitreous to dull; Crystal structure: Phaneric, coarse-grained texture; Specific Gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper appearance (black and white speckled)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper appearance (black and white speckled); Luster: Vitreous to dull; Crystal structure: Phaneric, coarse-grained texture; Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the slow cooling of magmatic liquid below the Earth's surface, typically in subduction zone settings where basaltic magma interacts with continental crust.
Uses & applications
Used as a dimension stone in construction, building facades, decorative aggregate, and road metal. Historically used by ancient civilizations like the Egyptians and Maya for statues, vessels, and tools.
Geological facts
Famous for its durability and being softer than granite yet tougher to carve, diorite is often called 'seven-hitter' by stone masons because it can blunt chisels quickly. The 'Wadi Hammamat' diorite was heavily quarried in ancient Egypt.
Field identification & locations
Identified by its balanced 50-50 mix of light-colored plagioclase feldspar and dark-colored minerals like hornblende and biotite, giving it a characteristic salt-and-pepper look. Found worldwide in major mountain-building belts.
