igneous
Basalt with Quartz/Calcite Veining
Basalt (principally Plagioclase and Pyroxene)
Hardness: 6-7 (basalt matrix); Color: Dark grey to black with white veining; Luster: Dull/earthy; Structure: Aphanitic (fine-grained) with secondary vein filling; Specific Gravity: 2.8-3.0
- Hardness
- 6-7 (basalt matrix)
- Color
- Dark grey to black with white veining
- Luster
- Dull/earthy
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Physical properties
Hardness: 6-7 (basalt matrix); Color: Dark grey to black with white veining; Luster: Dull/earthy; Structure: Aphanitic (fine-grained) with secondary vein filling; 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. Often found in seafloor crust and volcanic plateaus. White veins represent secondary mineral deposition from hydrothermal fluids.
Uses & applications
Commonly used as crushed aggregate in construction, road base, and railroad ballast. Larger decorative pieces are used in landscaping.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The white veins indicate the rock was once fractured and had mineral-rich water flowing through those cracks.
Field identification & locations
Identify in the field by its dark, dense, fine-grained texture. It will not scratch easily with steel. Found globally in volcanic regions or in glacial till and riverbeds.
