igneous
Diorite (Salt and Pepper Rock)
Diorite
Hardness: 6-7 on Mohs scale; Color: Black and white speckled; Luster: Dull to sub-vitreous; Structure: Phaneritic (coarse-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- Black and white speckled
- Luster
- Dull to sub-vitreous
Identified More igneous →
Explore Diorite (Salt and Pepper Rock) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on Mohs scale; Color: Black and white speckled; Luster: Dull to sub-vitreous; Structure: Phaneritic (coarse-grained); Specific Gravity: 2.8-3.0
Formation & geological history
Formed by the slow cooling of intermediate-composition magma beneath the Earth's surface (intrusive). Commonly found in volcanic arcs and mountain-building zones above subduction zones.
Uses & applications
Used as a base material in construction, crushed stone for roads, and occasionally as a polished decorative stone for countertops or monuments. Historically used for ancient carvings/statues due to its hardness.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for sculpture because it is extremely hard and durable; the Code of Hammurabi was famously inscribed on a diorite stele.
Field identification & locations
Identify by the distinct 'salt and pepper' appearance created by white plagioclase feldspar and dark amphibole or biotite minerals. Found in mountainous or coastal areas with tectonic history.
