igneous
Basalt Pebble
Basalt
Hardness: 6 (Mohs scale); Color: Dark gray to black (weathered to dull gray); Luster: Dull/Matte; Structure: Aphanitic (fine-grained); Specific Gravity: 2.8–3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark gray to black (weathered to dull gray)
- Luster
- Dull/Matte
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark gray to black (weathered to dull gray); Luster: Dull/Matte; 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 or marine erosion.
Uses & applications
Crushed basalt is used in construction for road base and railroad ballast. Highly polished stones are used in hot stone massage and decorative landscaping.
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 extensively on the Moon and Mars.
Field identification & locations
Identify in the field by its dark, heavy, fine-grained nature and lack of visible crystals. Commonly found on beaches near volcanic coastlines or in riverbeds draining volcanic highlands.
