igneous
Diorite (Porphyritic/Water-worn Pebble)
Diorite
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper look with speckled grey, black, and light brown/reddish mineral grains. Luster: Dull to sub-vitreous. Texture: Phaneritic to porphyritic. Specific gravity: 2.8 - 3.0.
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Salt-and-pepper look with speckled grey, black, and light brown/reddish mineral grains. Luster: Dull to sub-vitreous. Texture: Phaneritic to porphyritic. Specific gravity: 2.8 - 3.0.
Formation & geological history
Formed by the slow cooling of intermediate magma beneath the Earth's surface (intrusive igneous). Subsequently eroded, smoothed, and rounded by water action in riverbeds or ocean shores.
Uses & applications
Used in construction as crushed stone, dimension stone, building facades, and decorative river pebbles for landscaping.
Geological facts
Diorite was used in ancient Egypt and Mesopotamia for carving detailed sculptures, as it is extremely hard and durable; the famous Code of Hammurabi stele is carved into diorite.
Field identification & locations
Identified by its distinctive speckled 'salt-and-pepper' appearance containing a mix of light plagioclase feldspar and dark amphibole or pyroxene minerals. Found widely in volcanic arc environments and mountainous regions worldwide.
