igneous
Diorite
Intrusive Igneous Rock (Intermediate Composition)
Hardness: 6-7 Mohs; Color: Salt-and-pepper (mottled black and white); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Presents as varied mineral cleavage; Specific Gravity: 2.8 - 3.0.
- Hardness
- 6-7 Mohs
- Color
- Salt-and-pepper (mottled black and white)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (mottled black and white); Luster: Dull to sub-vitreous; Crystal structure: Phaneritic (coarse-grained); Cleavage: Presents as varied mineral cleavage; Specific Gravity: 2.8 - 3.0.
Formation & geological history
Formed from the slow cooling of magma beneath the Earth's surface in volcanic arcs and mountain building zones. It is an intermediate rock between granite and gabbro, often found in continental crust environments ranging from Precambrian to Cenozoic ages.
Uses & applications
Commonly used as a base material in road construction, building stone, and dimension stone for pavers or countertops. Historically used by ancient civilizations for sculpture due to its extreme durability.
Geological facts
Famous ancient artifacts, such as the Code of Hammurabi on a diorite stele and various Egyptian statues, were carved from this rock because it is harder than granite and holds detail well.
Field identification & locations
Identify in the field by its distinctive 'Dalmatian' appearance: a roughly equal mix of light plagioclase feldspar and dark minerals like hornblende or biotite. It lacks the visible quartz typical of granite. Found worldwide in mountain roots (e.g., Andes, Alps).
