igneous
Basalt with Quartz/Quartzite Veins
Aphanitic Mafic Volcanic Rock with Siliceous Infillings
Hardness: 6-7 (Mohs scale), Color: Dark grey to black matrix with tan/white veins, Luster: Dull/Earthy matrix with Vitreous veins, Structure: Fine-grained (aphanitic) matrix, Specific Gravity: 2.8-3.0
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Dark grey to black matrix with tan/white veins, Luster: Dull/Earthy matrix with Vitreous veins, Structure: Fine-grained (aphanitic) matrix, Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the surface. The linear veins formed later as hydrothermal fluids rich in silica filled fractures in the cooling rock and crystallized.
Uses & applications
Largely used as crushed stone for aggregate in construction, road base, and railroad ballast. This specific piece is a river-worn decorative specimen.
Geological facts
Basalt is the most common rock type in Earth's crust and makes up the entirety of the ocean floor. The veins represent ancient 'scars' where the rock cracked and healed through geological fluid circulation.
Field identification & locations
Identified by its heavy weight, dark color, and the presence of prominent protruding veins (which are harder and erode slower than the host rock). Commonly found in volcanic regions and riverbeds.
