igneous
Weathered gray-green igneous rock, likely basalt or andesite
Fine-grained mafic to intermediate volcanic rock; commonly plagioclase ± pyroxene, amphibole, and alteration minerals
AI-generated identification · may be incorrectHardness about 5.5–6.5 Mohs; gray-green, dull to weakly earthy luster, massive and fine-grained with no obvious cleavage. The rounded, pitted surface indicates weathering; exact identification would require a fresh face or testing.
Identified More igneous →
Explore Weathered gray-green igneous rock, likely basalt or andesite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 5.5–6.5 Mohs; gray-green, dull to weakly earthy luster, massive and fine-grained with no obvious cleavage. The rounded, pitted surface indicates weathering; exact identification would require a fresh face or testing.
Formation & geological history
Formed when lava cooled rapidly at or near Earth’s surface, generally during the Cenozoic or older volcanic episodes; weathering and transport rounded the specimen.
Uses & applications
Used as crushed aggregate, road metal, riprap, and building stone; attractive polished pieces may be collected, though this example appears ordinary.
Geological facts
Basalt is the most widespread volcanic rock and commonly forms oceanic crust; green coloration can result from chlorite, epidote, or other alteration minerals.
Field identification & locations
Look for a dense, fine-grained texture, relatively high weight, and weak magnetism; basalt is typically darker and more magnetic, while andesite is commonly lighter. Common worldwide, especially volcanic regions and stream gravels.
