igneous
Vesicular basalt (likely weathered volcanic rock)
Basalt; primarily plagioclase feldspar, pyroxene, and possible olivine
AI-generated identification · may be incorrectLight gray, porous, and strongly weathered, with small vesicles and dull earthy luster; fine-grained crystalline texture. Mohs hardness is about 5–6; cleavage is generally absent, and specific gravity is typically 2.7–3.0, though weathering lowers it.
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Physical properties
Light gray, porous, and strongly weathered, with small vesicles and dull earthy luster; fine-grained crystalline texture. Mohs hardness is about 5–6; cleavage is generally absent, and specific gravity is typically 2.7–3.0, though weathering lowers it.
Formation & geological history
Formed when basaltic lava rapidly cooled at or near Earth’s surface, trapping gas bubbles; the pale appearance likely reflects surface alteration. Basalt commonly ranges from recent eruptions to rocks millions or billions of years old.
Uses & applications
Used as crushed aggregate, road base, building stone, and occasionally decorative material; this specimen has little jewelry value.
Geological facts
Basalt is the most common volcanic rock and makes up much of the oceanic crust. Vesicles may later become filled with zeolites, calcite, or quartz.
Field identification & locations
Identify it by its fine grain, dark-to-gray volcanic composition, irregular vesicles, and lack of visible large crystals; a fresh broken surface should be darker. Common near lava flows, volcanic islands, and oceanic crust.
