First published use of name. Intent to name not stated. Forms an intrusive mass more than 2 mi wide from vicinity of Silver Creek to northwest edge of map, Mohave Co, AZ in the Plateau sedimentary province. Geologic map. No type locality designated. Probably named for Moss mine in T20N, R20W. Is a pinkish-gray medium-grained porphyry. Porphyritic texture is not conspicuous. Recognizable phenocrysts are plagioclase as much as 1 cm long in a crystalline groundmass of pink feldspar, biotite, and amphibole. Under a microscope the larger phenocrysts of sodic plagioclase lie in a fine granular groundmass of cloudy orthoclase, quartz, biotite, amphibole with magnetite, apatite, titanite, and zircon. Chemical analyses. Is younger than Alcyone trachyte (first used) and Oatman andesite (first used). May be the intrusive equivalent of Gold Road latite (first used). Assigned a Tertiary age.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Is present in a north-northwest elongate stock, 3 x 6 km that intrudes Alcyone Formation (redescribed), Gold Road Dacite (redescribed), and Oatman Andesite. Mafic dikes of Moss intrude Times Porphyry. The stock is concentrically zoned with an outer monzodiorite (IUGS) border, an inner porphyritic tonalite to quartz monzonite margin, and a central tonalite-granodiorite core. Modal (IUGS) average of core is monzogranite. Both the porphyritic margin and the core have the same mineralogy; they are composed of plagioclase, potassium feldspar, quartz, biotite, and minor amounts of actinolitic hornblende, clinopyroxene, and orthopyroxene. Is alkalic to slightly alkalic. Is magnesium-rich. Biotite (K-Ar) from Moss yielded a 10.7 +/-0.5 Ma date; this is considered the minimum age. Has an 18.5 +/-2.5 Ma crystallization age. Age modified from Tertiary to Miocene. Chemical analyses. Mapped (geologic map) in north-central part of area, north of Oatman, Mohave Co, AZ in the Plateau sedimentary province.

Source: GNU records (USGS DDS-6; Denver GNULEX).