igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (black and white); Luster: Phaneritic (medium to coarse-grained crystals); Structure: Massive/granular; Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' (black and white)
- Luster
- Phaneritic (medium to coarse-grained crystals)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (black and white); Luster: Phaneritic (medium to coarse-grained crystals); Structure: Massive/granular; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface in volcanic arcs and mountain-building zones (subduction zones). It is intermediate in composition between granite and gabbro.
Uses & applications
Commonly used as crushed stone for road construction and drainage. High-quality specimens are used in architecture as dimension stone for countertops, tiles, and monuments.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for sculptures because of its extreme hardness; the Code of Hammurabi was famously inscribed on a diorite stele.
Field identification & locations
Identify in the field by its phaneritic texture and nearly equal balance of light plagioclase feldspar and dark minerals like hornblende or biotite. It lacks the pink potassium feldspar found in granite.
