igneous
Diorite river stone
Intermediate Plutonic Igneous Rock (Diorite)
Hardness: 6-7 (Mohs). Color: Salt and pepper appearance (mottled grey, black, and white). Luster: Dull to sub-vitreous. Texture: Phaneritic (coarse-grained). Composition: Primarily plagioclase feldspar, biotite, and hornblende.
- Hardness
- 6-7 (Mohs)
- Color
- Salt and pepper appearance (mottled grey, black, and white)
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs). Color: Salt and pepper appearance (mottled grey, black, and white). Luster: Dull to sub-vitreous. Texture: Phaneritic (coarse-grained). Composition: Primarily plagioclase feldspar, biotite, and hornblende.
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface in volcanic arcs and mountain-building zones. This specific specimen has been smoothed and rounded by long-term fluvial (river) erosion.
Uses & applications
Used as crushed stone for road construction, drainage, and landscaping. Polished diorite is sometimes used as a dimension stone for fireplace mantels and building facades.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for sculptures and tablets because of its extreme hardness; the famous Code of Hammurabi was inscribed on a diorite stele.
Field identification & locations
Identify in the field by its distinctive 'salt and pepper' look where the black and white minerals are roughly equal in size. Commonly found in riverbeds near mountainous igneous regions.
