igneous
Quartz Veined Basalt
Mafic Igneous Rock with Quartz (SiO2) intrusion
Hardness: 6-7 (Mohs), Color: Dark grey to black matrix with reddish-brown oxidation and a tan quartz vein, Luster: Dull to earthy, Structure: Aphanitic (fine-grained) matrix
- Luster
- Dull to earthy, Structure: Aphanitic (fine-grained) matrix
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Physical properties
Hardness: 6-7 (Mohs), Color: Dark grey to black matrix with reddish-brown oxidation and a tan quartz vein, Luster: Dull to earthy, Structure: Aphanitic (fine-grained) matrix
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The visible vein formed later when mineral-rich hydrothermal fluids filled a fracture in the cooling rock.
Uses & applications
Basalt is primarily used as crushed stone for construction, road base, and concrete aggregate. This specific specimen is of interest to amateur collectors for its contrasting mineral vein.
Geological facts
Basalt is the most common rock type in the Earth's crust and covers most of the ocean floor. The reddish hue on the surface is likely 'desert varnish' or iron oxide weathering.
Field identification & locations
Identify by its heavy weight (high density), dark color, and fine grain. Usually found in volcanic fields, riverbeds, or coastal areas. The protruding vein indicates the filling material is harder than the host rock.
