Mindat Description
Rocks tentatively identified as trachyte, with felsics comprising <20% quartz, <10%foids and plagioclase/alkali feldspar <2
Geoscience Ontology Description
Fine grained igneous rock than contains less than 90 percent mafic minerals, less than 10 percent feldspathoid mineral and less than 20 percent quartz in the QAPF fraction and has a plagioclase to total feldspar ratio less than 0.65. Mafic minerals typically include amphibole or mica; typically porphyritic. Includes rocks defined modally in QAPF fields 6, 7 and 8 (with subdivisions) or chemically in TAS Field T as trachyte or latite.