igneous
Diorite
Diorite
Phaneritic (coarse-grained) texture; Salt and pepper appearance (black and white); Hardness: 6-7 Mohs; Luster: Vitreous to dull; Composition: Plagioclase feldspar and Hornblende or Biotite.
- Hardness
- 6-7 Mohs
- Luster
- Vitreous to dull
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Physical properties
Phaneritic (coarse-grained) texture; Salt and pepper appearance (black and white); Hardness: 6-7 Mohs; Luster: Vitreous to dull; Composition: Plagioclase feldspar and Hornblende or Biotite.
Formation & geological history
Formed from the slow cooling of magma beneath the Earth's surface in volcanic arcs and subduction zones. Created primarily during the Phanerozoic Eon.
Uses & applications
Used as a base material in road construction, as building stone (often sold as 'black granite'), for floor tiles, and historically for statues and carvings.
Geological facts
One of the most famous diorite artifacts is the Code of Hammurabi, a black diorite stele etched with Babylonian laws. It is incredibly tough and difficult to carve without modern tools.
Field identification & locations
Identify in the field by the distinct 'salt and pepper' mixture of light and dark minerals without the high quartz content seen in granite. Common in mountainous regions with historical tectonic activity.
