igneous
Diorite (Pebble)
Diorite
Hardness: 6-7 on Mohs scale. Color: 'Salt and pepper' mixture of white plagioclase feldspar and dark hornblende or biotite. Luster: Dull to sub-vitreous. Structure: Phaneritic (coarse-grained).
- Hardness
- 6-7 on Mohs scale
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale. Color: 'Salt and pepper' mixture of white plagioclase feldspar and dark hornblende or biotite. Luster: Dull to sub-vitreous. Structure: Phaneritic (coarse-grained).
Formation & geological history
Formed by the slow cooling of magma beneath the Earth's surface (intrusive) in volcanic arcs and mountain-building zones. This specific specimen appears to be water-worn into a smooth pebble shape.
Uses & applications
Commonly used as crushed stone for road construction, building materials, and occasionally as decorative stone or 'black granite' in monuments.
Geological facts
Diorite is extremely tough and was used by ancient civilizations, such as the Egyptians and Sumerians, to carve durable statues and stelae, including the famous Code of Hammurabi.
Field identification & locations
Identify by its distinct black-and-white speckled appearance. In the field, it is harder than glass and lacks the visible quartz typical of granite.
