igneous
Diorite
Diorite (an intrusive igneous rock)
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper appearance (mix of black and white/gray). Luster: Phaneritic (visible crystals), dull to vitreous. Crystal structure: Medium to coarse-grained. Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt-and-pepper appearance (mix of black and white/gray)
- Luster
- Phaneritic (visible crystals), dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper appearance (mix of black and white/gray). Luster: Phaneritic (visible crystals), dull to vitreous. Crystal structure: Medium to coarse-grained. 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 at subduction zones. It often happens in continental crust above a subducting oceanic plate.
Uses & applications
Used primarily as crushed stone for construction and base material for roads. High-quality specimens are polished for use as 'black granite' in countertops, tiles, and monuments.
Geological facts
Diorite was used by the Ancient Egyptians and Mesopotamians for sculpture because of its extreme hardness; the famous Code of Hammurabi is inscribed on a diorite stele.
Field identification & locations
Identified by its distinctive speckled appearance with roughly equal parts light and dark minerals. Look for it in mountain ranges and near larger granitic batholiths. It lacks the pinkish potassium feldspar found in granite.
