igneous
Diorite
Diorite (intermediate intrusive igneous rock)
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (mottled black and white); Luster: Phaneritic (crystalline/dull); Crystal structure: Coarse-grained phaneritic texture; Cleavage: Good in two directions (due to feldspar and amphibole).
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' (mottled black and white)
- Luster
- Phaneritic (crystalline/dull)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (mottled black and white); Luster: Phaneritic (crystalline/dull); Crystal structure: Coarse-grained phaneritic texture; Cleavage: Good in two directions (due to feldspar and amphibole).
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface in volcanic arcs or along subduction zones. It represents an intermediate composition between granite and gabbro.
Uses & applications
Used primarily as a crushed stone for construction and base material; occasionally polished for ornamental stone, countertops, or grave markers. Historically used for carving by ancient civilizations.
Geological facts
Ancient Egyptians used diorite to build tools and statues because of its extreme hardness. The Code of Hammurabi was famously inscribed on a pillar of diorite.
Field identification & locations
Identify in the field by its distinct speckling; unlike granite, it lacks or has very little visible quartz. It is commonly found in mountain roots (plutons) and at convergent plate boundaries.
