Andesite is a fine-grained, extrusive igneous rock composed mainly of plagioclase with other minerals such as hornblende, pyroxene and biotite. The specimen shown is about two inches (five centimeters) across.
This andesite is so packed with plagioclase and hornblende phenocrysts that it almost looks coarse-grained. The orangish coloring on some of the grains is iron staining.
This andesite is so packed with plagioclase and hornblende phenocrysts that it almost looks coarse-grained. The orangish coloring on some of the grains is iron staining.
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