igneous
Basalt Cobble
Vesicular Basalt (Mafic Extrusive)
Hardness: 6.0; Color: Dark grey to black, weathering to brown; Luster: Dull/Earthy; Structure: Fine-grained/aphanitic with visible vesicles (gas bubbles); Specific Gravity: 2.8 - 3.0
- Hardness
- 6
- Color
- Dark grey to black, weathering to brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6.0; Color: Dark grey to black, weathering to brown; Luster: Dull/Earthy; Structure: Fine-grained/aphanitic with visible vesicles (gas bubbles); Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. This specific specimen has been rounded through fluvial (water) or glacial erosion, typically over several thousand years.
Uses & applications
Commonly used as crushed stone for road base, concrete aggregate, railroad ballast, and ground cover. High-quality denser variants are used for floor tiles or stone monuments.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is the primary rock type on the Moon and Mars.
Field identification & locations
Identify in the field by its high density, dark color, and rounded shape if found near water. Look for small holes (vesicles). It is commonly found in volcanic fields, riverbeds, and coastal areas.
