igneous
Weathered gray-green basaltic rock
Basalt, likely altered to low-grade greenschist/amphibolite facies
AI-generated identification · may be incorrectFine- to medium-grained, dark gray-green, dull to slightly waxy luster, with weathered pale patches and possible faint mafic layering; mainly plagioclase and pyroxene, potentially chlorite, epidote, and actinolite. Hardness is approximately 5–6, with no obvious cleavage and specific gravity around 2.8–3.1.
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Physical properties
Fine- to medium-grained, dark gray-green, dull to slightly waxy luster, with weathered pale patches and possible faint mafic layering; mainly plagioclase and pyroxene, potentially chlorite, epidote, and actinolite. Hardness is approximately 5–6, with no obvious cleavage and specific gravity around 2.8–3.1.
Formation & geological history
Likely formed as volcanic basalt from rapidly cooled mafic lava, probably during the Mesozoic or older; the green alteration suggests later hydrothermal or low-grade metamorphic modification. Exact age and classification require thin-section or chemical analysis.
Uses & applications
Commonly used as crushed aggregate, road metal, railroad ballast, riprap, and building stone; attractive polished pieces may serve as decorative stone. It is generally inexpensive as a collector specimen.
Geological facts
Basalt is the most abundant volcanic rock and commonly forms oceanic crust and extensive lava flows. Green coloration often reflects secondary chlorite, epidote, or actinolite rather than the original basalt minerals.
Field identification & locations
Identify by its dark fine-grained texture, high density, lack of visible quartz, and occasional vesicles or plagioclase crystals; distinguish it from greenstone or amphibolite by laboratory texture and mineral identification. Common worldwide, especially in volcanic terrains and ophiolite belts.
