igneous
Basalt with Quartz Vein
Extrusive igneous rock with SiO2 hydrothermal vein
AI-generated identification · may be incorrectHardness of 6-7 for the vein and 5-6 for the host; dark gray to black color with a white/tan central vein; dull to vitreous luster; aphanitic to microcrystalline structure.
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Physical properties
Hardness of 6-7 for the vein and 5-6 for the host; dark gray to black color with a white/tan central vein; dull to vitreous luster; aphanitic to microcrystalline structure.
Formation & geological history
Formed by the rapid cooling of mafic lava at Earth's surface, later fractured and filled by hydrothermal silica-rich fluids.
Uses & applications
Used primarily in aggregate for construction, road base, and geological education.
Geological facts
Veins in volcanic rocks like this indicate secondary hydrothermal activity long after the initial lava flow solidified.
Field identification & locations
Identify in the field by contrasting dark, fine-grained volcanic matrix cut by a pale, hard quartz or carbonate vein.
