igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 (Mohs); Color: Mottled black and white ('salt and pepper'); Luster: Phaneritic (crystalline), dull to sub-glassy; Structure: Coarse-grained; Cleavage: Good in two directions via feldspar and hornblende.
- Hardness
- 6-7 (Mohs)
- Color
- Mottled black and white ('salt and pepper')
- Luster
- Phaneritic (crystalline), dull to sub-glassy
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Physical properties
Hardness: 6-7 (Mohs); Color: Mottled black and white ('salt and pepper'); Luster: Phaneritic (crystalline), dull to sub-glassy; Structure: Coarse-grained; Cleavage: Good in two directions via feldspar and hornblende.
Formation & geological history
Formed through the slow cooling of magma beneath the Earth's surface in volcanic arches or subduction zones. It has an intermediate chemical composition between granite and gabbro.
Uses & applications
Used primarily in the construction industry as crushed stone for road bases and drainage. When polished, it is used as a dimension stone for floor tiles, granite-style countertops, and building facing.
Geological facts
Diorite was an extremely popular stone for sculpture in ancient Egypt and Mesopotamia because it is very hard and durable; the famous Code of Hammurabi was inscribed on a diorite stele.
Field identification & locations
Identify by its 'salt and pepper' appearance with roughly equal amounts of dark minerals (hornblende/biotite) and light minerals (plagioclase feldspar). Look for interlocking crystals visible to the naked eye.
