Andesite refers to an extrusive dark greyish rock that consists of plagioclase, oligoclase or feldspar. The rock may also contain one or more mafic minerals such as hornblende or biotite. The rock is usually fine-grained.
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what is the definition of andesite
a dark-colored volcanic rock composed essentially of plagioclase feldspar and one or more mafic minerals, as hornblende or biotite.