igneous
Basalt River Pebble (with possible Pyrite/Mineralization)
Basalt (Mafic volcanic rock)
Hardness: 5-6 Mohs; Color: Dark grey, greenish-black, with metallic yellowish glints; Luster: Dull to sub-metallic; Structure: Fine-grained/Aphanitic; Specific gravity: 2.8-3.0
- Hardness
- 5-6 Mohs
- Color
- Dark grey, greenish-black, with metallic yellowish glints
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs; Color: Dark grey, greenish-black, with metallic yellowish glints; Luster: Dull to sub-metallic; Structure: Fine-grained/Aphanitic; Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava. This specimen shows significant water-wearing (river erosion) and secondary mineral staining or pyrite inclusions.
Uses & applications
Commonly used as crushed stone in construction, road base, and as a durable decorative landscape stone. Minor metallic inclusions make it a subject for amateur mineral collectors.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. When eroded in rivers, it forms smooth, heavy 'cobbles' or 'pebbles'.
Field identification & locations
Identify by its dark color, heavy weight for its size, fine grain, and smooth water-worn surface. Often found in riverbeds or volcanic regions. Metallic flecks may indicate sulfur or iron mineralization.
