igneous
Diorite
Diorite (Intermediate intrusive igneous rock)
Hardness: 6-7 on the Mohs scale. Color: Mottled 'salt and pepper' appearance (black and white). Luster: Phaneritic (crystalline). Crystal Structure: Coarse-grained phaneritic texture. Cleavage: Good in two directions via feldspar components. Specific Gravity: 2.8-3.0.
- Hardness
- 6-7 on the Mohs scale
- Color
- Mottled 'salt and pepper' appearance (black and white)
- Luster
- Phaneritic (crystalline)
Identified More igneous →
Explore Diorite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on the Mohs scale. Color: Mottled 'salt and pepper' appearance (black and white). Luster: Phaneritic (crystalline). Crystal Structure: Coarse-grained phaneritic texture. Cleavage: Good in two directions via feldspar components. Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the slow cooling of magma beneath the Earth's surface in volcanic arcs and mountain-building zones (subduction zones). It is typically of Phanerozoic age but can be found in older Precambrian shields.
Uses & applications
Commonly used as a base material in construction, crushed stone for roads, and occasionally as a polished 'granite' for countertops and floor tiles. Historically used by ancient civilizations for sculpture and tools 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 on a 7-foot tall stele made of polished black diorite. It is often confused with granite but lacks significant quartz content.
Field identification & locations
Identify in the field by its distinctive 'salt and pepper' look where the light (plagioclase feldspar) and dark (hornblende or biotite) minerals are roughly equal. Found in large mountain ranges like the Andes or the Cascades. Collectors look for pieces with large, well-defined amphibole crystals.
