- a dark-colored volcanic rock composed essentially of plagioclase feldspar and one or more mafic minerals, as hornblende or biotite.
- a fine-grained tan or grey volcanic rock consisting of plagioclase feldspar, esp andesine, amphibole, and pyroxene
- A gray, fine-grained volcanic rock. Andesite consists mainly of sodium-rich plagioclase feldspar and one or more mafic minerals such as biotite, hornblende, or pyroxene. It often contains small, visible crystals (phenocrysts) of plagioclase.