igneous
Basalt with Quartz Vein
Aphanitic Mafic Igneous Rock with Silicon Dioxide (SiO2) intrusion
Hardness: 6 (basalt) to 7 (quartz); Color: Dark grey/black matrix with white/tan vein; Luster: Dull/earthy matrix with vitreous vein; Texture: Fine-grained; Specific Gravity: ~2.9-3.0.
- Hardness
- 6 (basalt) to 7 (quartz)
- Color
- Dark grey/black matrix with white/tan vein
- Luster
- Dull/earthy matrix with vitreous vein
Identified More igneous →
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Physical properties
Hardness: 6 (basalt) to 7 (quartz); Color: Dark grey/black matrix with white/tan vein; Luster: Dull/earthy matrix with vitreous vein; Texture: Fine-grained; Specific Gravity: ~2.9-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. The vein formed later through hydrothermal activity where mineral-rich water filled fractures in the rock and precipitated quartz.
Uses & applications
Basalt is used heavily in construction as aggregate, road base, and railroad ballast. Veined specimens are mainly of interest to amateur collectors or as educational samples.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. Small quartz veins like this one are often footprints of ancient heated water movement through the crust.
Field identification & locations
Identify by the heavy weight (density), dark color, and fine grain size. The vein will be significantly harder than the host rock. Commonly found in volcanic fields, riverbeds, and glacial tills.
