igneous
Diorite
Phaneritic intermediate plutonic rock
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (mottled black and white/grey); Luster: Phaneritic (crystalline visible to the eye); Crystal Structure: Granular/Equigranular; Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt and pepper (mottled black and white/grey)
- Luster
- Phaneritic (crystalline visible to the eye)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Salt and pepper (mottled black and white/grey); Luster: Phaneritic (crystalline visible to the eye); Crystal Structure: Granular/Equigranular; 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 has an intermediate composition between granite and gabbro.
Uses & applications
Used as a base material in construction, road building, and as ornamental stone for floor tiles, granite-style countertops, and monument carving.
Geological facts
Diorite was used by ancient civilizations for sculpture 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 distinctive 'salt and pepper' appearance and lack of visible quartz (unlike granite). Found in large batholiths in mountain ranges like the Andes or Cascades.
