igneous
Likely weathered blue-gray basalt
Basalt, a fine-grained mafic volcanic rock; commonly plagioclase + pyroxene ± olivine and iron oxides
AI-generated identification · may be incorrectGray-blue, dull to weakly vitreous, fine-grained and rounded by weathering; likely Mohs 5–6, with no obvious cleavage and specific gravity about 2.8–3.1. The pale patches may be weathered feldspar or secondary alteration minerals.
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Physical properties
Gray-blue, dull to weakly vitreous, fine-grained and rounded by weathering; likely Mohs 5–6, with no obvious cleavage and specific gravity about 2.8–3.1. The pale patches may be weathered feldspar or secondary alteration minerals.
Formation & geological history
Basalt forms when low-silica lava cools rapidly at or near Earth’s surface, commonly in volcanic fields. The reported location in northern Ethiopia lies within the East African Rift, where young Cenozoic volcanic rocks are abundant.
Uses & applications
Used extensively as crushed aggregate, road metal, riprap, paving stone, and building stone; generally little jewelry value unless unusually vesicular, altered, or polished.
Geological facts
Its blue-gray color is compatible with altered or weathered rift basalt, but the photograph alone cannot exclude fine-grained andesite or a blue-gray metamorphic rock.
Field identification & locations
Look for a dense, fine texture, tiny dark pyroxene grains, pale feldspar specks, and possible vesicles; it should not fizz strongly in dilute acid. A streak, hardness, magnetism, and fresh broken surface would improve identification. Common around Ethiopian Rift volcanic terrains.
