igneous
Basalt River Pebble
Basalt (Mafic volcanic rock)
Hardness: 5-6 (Mohs); Color: Dark grey to charcoal/black with slight weathering patinas; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey to charcoal/black with slight weathering patinas
- Luster
- Dull/Matte
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey to charcoal/black with slight weathering patinas; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specific specimen has been rounded by fluvial (river) or coastal erosion.
Uses & applications
Mainly used as aggregate in construction (roads and concrete), but often collected as smooth 'worry stones' or decorative river rock in landscaping.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It also exists on the Moon and Mars.
Field identification & locations
Identified in the field by its high density, dark color, and lack of visible crystals. Commonly found in volcanic regions, river beds, and along coastal beaches.
