igneous
Diorite
Diorite
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (black and white/grey); Luster: Sub-vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Composition: Mostly plagioclase feldspar and hornblende/biotite.
- Hardness
- 6-7 on Mohs scale
- Color
- 'Salt and pepper' (black and white/grey)
- Luster
- Sub-vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: 'Salt and pepper' (black and white/grey); Luster: Sub-vitreous to dull; Crystal structure: Phaneritic (coarse-grained); Composition: Mostly plagioclase feldspar and hornblende/biotite.
Formation & geological history
Formed through the slow cooling of magma deep beneath the Earth's surface (intrusive), typically above subduction zones or in volcanic arc environments. Most specimens range from hundreds of millions to billions of years old.
Uses & applications
Used in construction as crushed stone or 'black granite' for countertops, floor tiles, and pavers. Historically used in ancient civilizations for sculpture and steles due to its extreme hardness.
Geological facts
The Code of Hammurabi, one of the oldest deciphered writings of significant length in the world, was inscribed onto a seven-foot-tall slab of black diorite. It is often referred to as the 'middle ground' between granite and gabbro.
Field identification & locations
Identify in the field by its distinctive speckled appearance where dark and light minerals are present in roughly equal amounts. It lack the visible quartz crystals common in granite. Commonly found in roots of mountain ranges.
