igneous
Basalt Pebble
Basalt
Hardness: 5-6 Mohs. Color: dark gray, black, or dark brown. Luster: dull to matte. Crystal structure: fine-grained (aphanitic) or porphyritic. Specific gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- dark gray, black, or dark brown
- Luster
- dull to matte
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Physical properties
Hardness: 5-6 Mohs. Color: dark gray, black, or dark brown. Luster: dull to matte. Crystal structure: fine-grained (aphanitic) or porphyritic. 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 surface of a terrestrial planet or moon. This specific pebble is a water-rounded clast likely from an ocean or river environment.
Uses & applications
Commonly used in construction for aggregate, road base, and concrete. Smooth pebbles are popular in landscaping, aquarium decor, and hot stone massage therapy.
Geological facts
Basalt is the most common rock type in the Earth's crust, covering most of the ocean floor and often forming iconic columnar structures like the Giant's Causeway.
Field identification & locations
Identify in the field by its high density/weight, dark color, and lack of visible grains with the naked eye. Often found along coastlines with volcanic history.
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