The mineral assembly is usually abundant feldspathoids ( nepheline or leucite ), plagioclase, and augite, together with olivine and lesser iron-titanium oxides such as ilmenite and magnetite-ulvospinel; minor alkali feldspar may be present, as illustrated by the position of the field for basanite in the QAPF diagram.
12.
The completed rock analysis is first to be interpreted in terms of the rock-forming minerals which might be expected to be formed when the magma crystallizes, e . g ., quartz feldspars, olivine, akermannite, Feldspathoids, magnetite, corundum, and so on, and the rocks are divided into groups strictly according to the relative proportion of these minerals to one another.
13.
Mitchell has suggested that rocks belonging to the " lamprophyre facies " are characterized by the presence of phenocrysts of mica and / or amphibole together with lesser clinopyroxene and / or melilite set in a groundmass which may consist ( either singly or in various combinations ) of plagioclase, alkali feldspar, feldspathoids, carbonate, monticellite, melilite, mica, amphibole, pyroxene, perovskite, Fe-Ti oxides and glass.
