igneous
White-veined basalt (likely basalt with quartz/calcite vein)
Basalt, chiefly plagioclase feldspar and pyroxene, with a light-colored secondary vein of quartz or calcite
AI-generated identification · may be incorrectDark gray, fine-grained, dull to slightly vitreous rock with a contrasting white irregular vein; basalt hardness is about 5–6 Mohs, while quartz is 7 and calcite is 3. Crystal grains are mostly microscopic, so cleavage is not obvious.
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Physical properties
Dark gray, fine-grained, dull to slightly vitreous rock with a contrasting white irregular vein; basalt hardness is about 5–6 Mohs, while quartz is 7 and calcite is 3. Crystal grains are mostly microscopic, so cleavage is not obvious.
Formation & geological history
Formed when mafic lava cooled rapidly at or near Earth’s surface; the white material likely crystallized later from mineral-rich fluids in a fracture. Basalt ranges from Precambrian to modern age, but this specimen’s age cannot be determined visually.
Uses & applications
Used widely as crushed aggregate, road stone, riprap, and building stone; attractive pieces are collected or used decoratively, though this specimen has limited gem value.
Geological facts
The pale vein may fizz with dilute hydrochloric acid if it is calcite, but will not fizz if quartz. The dark host’s dense, fine texture and iron-rich color are typical of basalt.
Field identification & locations
Common in volcanic regions, oceanic crust, and flood-basalt provinces; likely localities include Hawaii, Iceland, the Columbia River Basalt, and many other volcanic terrains. A fresh surface, acid test, and hardness test can distinguish calcite from quartz.
