igneous
Diorite
Phaneritic Intermediate Plutonic Rock (Diorite)
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (speckled black and white). Luster: Dull to sub-vitreous. Structure: Phaneritic (coarse-grained). Cleavage: Present in feldspar and amphibole minerals. Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- Salt-and-pepper (speckled black and white)
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper (speckled black and white). Luster: Dull to sub-vitreous. Structure: Phaneritic (coarse-grained). Cleavage: Present in feldspar and amphibole minerals. Specific Gravity: 2.8-3.0.
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface (intrusive) in volcanic arcs or above subduction zones. Typically formed during orogenic (mountain-building) events across various geological eras.
Uses & applications
Used primarily as a construction material (crushed stone) for roads and drainage. In polished form, it is used for countertops, floor tiles, and grave markers. Historically used for carving by ancient civilizations.
Geological facts
Ancient Egyptians and Maya civilizations used diorite for statues and stelae because of its extreme hardness. The famous Code of Hammurabi was inscribed on a large diorite stele.
Field identification & locations
Identify in the field by its speckled 'salt and pepper' appearance and lack of visible quartz (unlike granite). Found in areas with mountain-building history like the Andes, the Alps, and the Scottish Highlands.
