igneous
Diorite
Intrusive Igneous Diorite
Hardness: 6-7 (Mohs); Color: Black and white (salt and pepper appearance); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Composition: Large amounts of plagioclase feldspar and hornblende/biotite.
- Hardness
- 6-7 (Mohs)
- Color
- Black and white (salt and pepper appearance)
- Luster
- Subvitreous to dull
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs); Color: Black and white (salt and pepper appearance); Luster: Subvitreous to dull; Crystal structure: Phaneritic (coarse-grained); Composition: Large amounts of plagioclase feldspar and hornblende/biotite.
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface (intrusive) in volcanic arcs and mountain building zones. It is commonly associated with subduction zones.
Uses & applications
Used primarily as a crushed stone for road construction and drainage. It is also used as a decorative building stone (granite-like) for countertops, floor tiles, and facings. In ancient times, it was used for sculpture due to its hardness.
Geological facts
The Code of Hammurabi, one of the oldest deciphered writings of significant length in the world, was inscribed on a 7-foot tall black diorite stele. It is often mistake for granite but contains very little to no quartz.
Field identification & locations
Identified by its speckled black-and-white 'dalmatian' appearance with crystals large enough to see with the naked eye. It is found in large mountain ranges like the Andes or the Alps.
