igneous
Fine-grained gray-green rock, likely basaltic or volcanic stone
Probable basalt or microcrystalline mafic igneous rock; exact identification requires a fresh surface and testing
AI-generated identification · may be incorrectTypically 5–6 Mohs, dull to faintly earthy luster, dark gray-green color, very fine interlocking crystals, and no obvious cleavage; likely composed mainly of plagioclase and pyroxene with alteration minerals.
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Physical properties
Typically 5–6 Mohs, dull to faintly earthy luster, dark gray-green color, very fine interlocking crystals, and no obvious cleavage; likely composed mainly of plagioclase and pyroxene with alteration minerals.
Formation & geological history
Likely formed when mafic lava cooled rapidly at or near Earth’s surface, generally from geologically young to ancient volcanic activity. The greenish tone may reflect weathering or chlorite/olivine alteration.
Uses & applications
Common basalt is used as aggregate, roadstone, riprap, paving, and construction material; this small weathered piece has little commercial or jewelry value.
Geological facts
Its rounded edges and uniform texture suggest stream or surface abrasion. A fresh broken face, streak, magnetism test, and a hand lens would distinguish basalt from greenstone, slate, or dense sedimentary rock.
Field identification & locations
Common in volcanic regions worldwide, including India, Iceland, Hawaii, the western United States, and oceanic crust. Look for dark color, high density, fine grain, and occasional tiny feldspar crystals; avoid calling it basalt if it shows layering or strong foliation.
