igneous
Diorite
Diorite (an intrusive igneous rock)
Hardness: 6-7 Mohs; Color: Salt and pepper (mottled black and white); Luster: Sub-vitreous to dull; Structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspar and amphibole minerals; Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 Mohs
- Color
- Salt and pepper (mottled black and white)
- Luster
- Sub-vitreous to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Salt and pepper (mottled black and white); Luster: Sub-vitreous to dull; Structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspar and amphibole minerals; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through the slow cooling of silicate magma below the Earth's surface (intrusive), typically in volcanic arcs and mountain-building zones (subduction zones). It consists of plagioclase feldspar, biotite, and hornblende.
Uses & applications
Used primarily as a decorative stone in architecture and construction, such as floor tiles, countertops, and paving. Historically used by ancient civilizations for sculpture due to its extreme durability.
Geological facts
The Code of Hammurabi was inscribed on a massive basaltic-diorite stele. It is often referred to as salt and pepper rock because of its distinct mineral speckling.
Field identification & locations
Identify by its coarse grain and lack of visible quartz compared to granite. Found in large mountain ranges like the Andes or Alps. Collectors should look for balanced mineral distribution.
