igneous
Diorite
Phaneritic intermediate plutonic rock
Hardness: 6-7 Mohs; Color: Salt and pepper (black and white); Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained); Composition: Plagioclase feldspar, hornblende, and biotite.
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper (black and white)
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (black and white); Luster: Dull to vitreous; Structure: Phaneritic (coarse-grained); Composition: Plagioclase feldspar, hornblende, and biotite.
Formation & geological history
Formed by the slow cooling of silicate magma below the Earth's surface in the roots of volcanic arcs and subduction zones.
Uses & applications
Used as a decorative stone, crushed stone for road construction, and historically for sculpture and masonry because of its durability.
Geological facts
The Code of Hammurabi was inscribed on a large polished slab of black diorite. It is often confused with granite but contains little to no quartz.
Field identification & locations
Identified by its phaneritic texture and lack of visible quartz crystals compared to granite; commonly found in mountain belts like the Andes or Cascades.
