igneous
Diorite
Diorite
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (mottled black and white/gray); Luster: Phaneritic (visible crystals), Dull to sub-vitreous; Crystal Structure: Coarse-grained intrusive; Cleavage: Often exhibits two directions from amphibole/feldspar.
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' (mottled black and white/gray)
- Luster
- Phaneritic (visible crystals), Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (mottled black and white/gray); Luster: Phaneritic (visible crystals), Dull to sub-vitreous; Crystal Structure: Coarse-grained intrusive; Cleavage: Often exhibits two directions from amphibole/feldspar.
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
Used primarily as a crushed stone for construction, road base, and drainage. When polished, it is used as a dimension stone for flooring, counter tops, and monuments.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for sculptures and inscriptions because of its extreme hardness; the famous Code of Hammurabi was carved onto a Diorite stele.
Field identification & locations
Identify by its coarse-grained texture and roughly equal mix of light (plagioclase feldspar) and dark (hornblende/biotite) minerals. Commonly found in roots of mountain ranges like the Andes or Cascades.
