igneous
Basalt with Calcite Veins
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale for the rock matrix (lower for calcite veins); dark gray to black color; fine-grained, aphanitic texture; dull to sub-vitreous luster; conchoidal to uneven fracture; specific gravity around 2.8 - 3.0.
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Physical properties
Hardness of 6 on the Mohs scale for the rock matrix (lower for calcite veins); dark gray to black color; fine-grained, aphanitic texture; dull to sub-vitreous luster; conchoidal to uneven fracture; 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. Veins are typically secondary mineral deposits formed by hydrothermal fluids precipitating calcite into fractures.
Uses & applications
Used in construction, aggregate for road building, production of rock wool insulation, and as dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and also makes up extensive volcanic provinces on continents, as well as being found on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained appearance, often featuring lighter mineral inclusions or veins like the white calcite shown here. Found worldwide in volcanic regions.
