igneous
Basalt with Calcite Veining
Aphanitic Mafic Igneous Rock (primarily Plagioclase and Pyroxene)
Hardness: 6 (Mohs), Color: Dark grey to black with white veins, Luster: Dull/Earthy (matrix) to Vitreous (veining), Structure: Fine-grained aphanitic, Cleavage: None/Irregular
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Physical properties
Hardness: 6 (Mohs), Color: Dark grey to black with white veins, Luster: Dull/Earthy (matrix) to Vitreous (veining), Structure: Fine-grained aphanitic, Cleavage: None/Irregular
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the surface of a planet or moon. The white veins represent secondary mineralization where fluids deposited minerals like calcite or quartz in fractures long after the rock solidified.
Uses & applications
Commonly used as aggregate in construction, road base, and concrete. Small specimens with interesting veining are kept as educational or decorative garden stones.
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 in abundance on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, heavy weight (high density), and fine grain. The presence of white veins that react with acid usually indicates calcite. Found globally in volcanic regions.
