igneous
Diorite
Diorite
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' mixture of black and white/grey; Luster: Phaneritic (crystalline/speckled); Crystal Structure: Prismatic/massive; Cleavage: Good in two directions; Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' mixture of black and white/grey
- Luster
- Phaneritic (crystalline/speckled)
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' mixture of black and white/grey; Luster: Phaneritic (crystalline/speckled); Crystal Structure: Prismatic/massive; Cleavage: Good in two directions; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through the slow cooling of magma beneath the Earth's surface (intrusive) in volcanic arcs and mountain building zones (subduction zones).
Uses & applications
Used primarily as crushed stone for road construction and as a decorative building stone known as 'black granite'. It is also used for carvings and sometimes polished for jewelry or collection.
Geological facts
Diorite is extremely hard and was used by ancient civilizations like the Egyptians and Mesopotamians for monumental sculptures, such as the famous Code of Hammurabi stele.
Field identification & locations
Identify in the field by its speckled, intermediate composition (more dark minerals than granite, fewer than gabbro). Look for it in mountainous regions or ancient magmatic roots. Common in the Andes Mountains and parts of the UK.
