On a purely chemical basis, an extrusive lamprophyre ( sp . " minette " ) might be classified as potassic trachybasalt, shoshonite, or latite using the total alkali-silica diagram ( see TAS classification ), or as absarokite, shoshonite, or banakite using a classification sometimes applied to potassium-rich lavas.
32.
In the US, chromian diopside localities are described in the serpentinite belt in northern California, in kimberlite in the Colorado-Wyoming State Line district, in kimberlite in the Iron Mountain district, Wyoming, in lamprophyre at Cedar Mountain in Wyoming, and in numerous anthills and outcrops of the Tertiary Bishop Conglomerate in the Green River Basin of Wyoming.
33.
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.
