GEOLOGICAL SPECIMENS MINERAL ANDESITE

• RM6335-01

Samples of andesite are typically gray to black volcanic rocks with visible crystals of plagioclase feldspar (often white) and hornblende (often black) embedded in a fine-grained groundmass. Other minerals like pyroxene and biotite may also be present. Some samples exhibit iron staining or other inclusions, and while the overall rock is fine-grained, the larger crystals, or phenocrysts, make it an example of porphyry