igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black in color, fine-grained to aphanitic texture, dull to sub-vitreous luster, specific gravity around 2.8 - 3.0.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black in color, fine-grained to aphanitic texture, dull to sub-vitreous luster, specific gravity around 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a planet or moon.
Uses & applications
Used in construction as crushed stone for road bases, railroad ballast, concrete aggregate, and sometimes as dimension stone or for decorative landscaping.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans. Similar dark volcanic rocks are also abundant on the surface of the Moon and Mars.
Field identification & locations
Found widely along beaches, riverbeds, and volcanic regions globally. It can be identified in the field by its dark color, heavy feel for its size, and dense, fine-grained texture.
