Geology and petrology of Tetilla Peak, Santa Fe County, New Mexico

Abstract

hypersthene going to hornblende; and (4) the appearance of Fe-Ti oxides and lighter-colored glass in the groundmass. Hornblende andesites are seen easily in hand specimen because of large prisms of hornblende phenocrysts that make up 4 to 11 percent of the mode. The dacite possesses a more glassy groundmass with only minor plagioclase crystallites and Fe-Ti oxide granules.