igneous
Diorite (River Cobble)
Intermediate phaneritic igneous rock
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white, gray, black); Luster: Dull (weathered) to vitreous; Structure: Phaneritic (coarse-grained crystals); Composition: Plagioclase feldspar, hornblende, and biotite mica.
- Hardness
- 6-7 Mohs
- Color
- Salt-and-pepper (white, gray, black)
- Luster
- Dull (weathered) to vitreous
Identified More igneous →
Explore Diorite (River Cobble) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 Mohs; Color: Salt-and-pepper (white, gray, black); Luster: Dull (weathered) to vitreous; Structure: Phaneritic (coarse-grained crystals); Composition: Plagioclase feldspar, hornblende, and biotite mica.
Formation & geological history
Formed through the slow cooling of magma beneath the Earth's surface in volcanic arcs or mountain-building regions. This specific specimen has been rounded and smoothed by water transport in a river or glacial environment.
Uses & applications
Commonly used as a base material in road construction, as dimension stone for buildings, and occasionally crushed for landscaping rock.
Geological facts
Diorite was used by ancient civilizations, such as the Babylonians, to carve stele and statues because of its extreme hardness and durability; the Code of Hammurabi is inscribed on a black basalt/diorite pillar.
Field identification & locations
Identifiable by its phaneritic texture with approximately equal amounts of light and dark minerals and a lack of visible quartz. Collectors can find these in riverbeds or glacial tills in mountainous regions.
