Olivine Pyroxene AndesiteAndesite is a type of finely crystalline rock of volcanic origin that typically consists of andesine or another plagioclase feldspar and one or more ferromagnesian minerals, such as pyroxene and olivine. This type of rock, which is common in the Andes Mountains from whence it gains its name, typically occurs in porphyries, large crystals of the feldspar or dark minerals it contains jutting out of a fine-grained matrix. |