An igneous rock, usually light gray in color and breaking with a rough surface. It consists chiefly of orthoclase feldspar with sometimes hornblende and mica.
A fine grained igneous rock consisting mainly of feldspars containing potassium, usually with mica, amphibole, and pyroxene but with little if any quartz. Sometimes glassy in nature. The fine grained equivalent of syenite.
Fine grained igneous rock equivalent in composition to a syenite. Contains a small amount of free quartz.
A group of fine-grained, generally porphyritic, extrusive igneous rocks having alkali feldspar and minor mafic minerals as the main components, and possibly a small amount of sodic plagioclase.
A light gray igneous rock with a rough surface consisting of orthoclase feldspar.
fine-grained volcanic rock of the alkaline series of intermediate rocks
volcanic leucocratic rock, without quartz crystals and containing potassic feldspar.
A fine-grained porphyritic volcanic rock, consisting mainly of alkali feldspar and minor mafic minerals; the extrusive equivalent of syenite
volcanic rock made up of potassium feldspars; other minerals such as plagioclase feldspars and quartz can also be present (the igneous homologue is called syenite)
a light-colored volcanic rock consisting chiefly of alkali feldspar, and also containing augite, biotite, or hornblende. [AHDOS
Trachyte is an igneous, volcanic rock with an aphanitic to porphyritic texture. The mineral assemblage is predominately potassium feldspar with relatively minor plagioclase. Either quartz or a feldspathoid such as nepheline may be a minor constituent, as shown by the defined position for trachyte on the QAPF diagram.