igneous
Basalt Pebble
Basaltic Igneous Rock
Hardness: 5-6 Mohs. Color: Blueish-gray to black with white plagioclase or quartz veining. Luster: Dull to sub-metallic. Structure: Fine-grained (aphanitic) matrix with visible weathering patterns. Specific Gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 5-6 Mohs. Color: Blueish-gray to black with white plagioclase or quartz veining. Luster: Dull to sub-metallic. Structure: Fine-grained (aphanitic) matrix with visible weathering patterns. Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specific specimen is a river-worn or beach-worn pebble, indicating it was shaped by fluvial or coastal erosion over thousands of years.
Uses & applications
Primarily used as decorative landscaping stone (river rock), road base, and as an aggregate in concrete when crushed. Smooth pebbles are popular in massage therapy and home decor.
Geological facts
Basalt is the most common rock in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon, Mars, and Venus. The white streaks are likely secondary mineral infillings like quartz or calcite that occurred after the rock formed.
Field identification & locations
Identify by its heavy weight, dark color, and smooth water-worn surface. Often found in volcanic regions near coastlines or in glacial river deposits. It won't scratch easily with a copper penny but can be scratched by a steel file.
