igneous
Basalt Pebble
Basalt (Mafic Igneous Rock)
Hardness: 6.0; Color: Dark grey to black; Luster: Dull or earthy when weathered; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull or earthy when weathered
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull or earthy when weathered; 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 specimen appears water-worn, indicating it was shaped by fluvial or coastal transport.
Uses & applications
Large-scale basalt is used for road base, concrete aggregate, and railroad ballast. Small pebbles are often used in landscaping or as decorative stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size (high density), and lack of visible crystals to the naked eye. Commonly found in volcanic regions and riverbeds.
