igneous
Basalt with Quartz Veining
Basalt (Mafic Extrusive Igneous Rock) with SiO2 (Silicon Dioxide) veins
Hardness: 6 (basalt) to 7 (quartz). Color: Dark gray to black matrix with white to off-white banding. Luster: Dull/earthy matrix with vitreous/glassy veins. Structure: Aphanitic (fine-grained) matrix with crystalline veins. Cleavage: Poor/Conchoidal.
- Hardness
- 6 (basalt) to 7 (quartz)
- Color
- Dark gray to black matrix with white to off-white banding
- Luster
- Dull/earthy matrix with vitreous/glassy veins
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Physical properties
Hardness: 6 (basalt) to 7 (quartz). Color: Dark gray to black matrix with white to off-white banding. Luster: Dull/earthy matrix with vitreous/glassy veins. Structure: Aphanitic (fine-grained) matrix with crystalline veins. Cleavage: Poor/Conchoidal.
Formation & geological history
Basalt forms from the rapid cooling of magnesium-rich and iron-rich lava. The quartz veins are secondary formations, created when hydrothermal fluids rich in silica circulated through cracks in the hardened basalt, cooling and crystallizing over millions of years.
Uses & applications
Basalt is primarily used in construction as aggregate, road base, and railroad ballast. While decorative, this specific specimen is most commonly used for landscaping or as a geological study sample.
Geological facts
Basalt is the most common rock type on Earth's crust and makes up most of the ocean floor. The white veins are permanent 'scars' indicating where the rock once fractured under tectonic pressure before being healed by mineral-rich water.
Field identification & locations
Identify by its heavy weight (high specific gravity), dark fine-grained appearance, and the way the white veins cut across the primary rock body. Found globally in volcanic regions or glacial till. Collectors look for sharp, high-contrast veining.
