First published use of name. Intent to name, source of name, type locality not stated. Name applied to a grayish granular rock in which aggregations of hornblende crystals in patches half an inch to 3 inches across are conspicuous. Texture is porphyritic. Phenocrysts of alkali feldspar common. Dark silicates nearly equal feldspar constituents in some occurrences. The groundmass is largely feldspathic, fine grained and granular, but may be coarse grained and holocrystalline. Some disseminated magnetite. Is related to the monzonite varieties of the early lamprophyres. Resembles the early monzonite porphyry of the Spanish Peaks system. Belongs to the Silver Mountain eruption center. Mapped in two masses in the west-central edge of the geologic map in Huerfano Co, CO in the Las Vegas-Raton basin. Assigned an Eocene and Neocene age.

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