Granite, informally called Mellen granite by many previous workers, shows crosscutting relations to Mineral Lake intrusion, but the two have indistinguishable U-Pb ages. Equigranular to porphyritic. Dark-gray to black. Plagioclase laths up to 1 cm, commonly strongly oriented. Olivine generally abundant and apatite is common accessory.
Accessory minerals are clinopyroxene, orthopyroxene, minor hornblende, apatite, and opaque minerals.
Dark-gray to black. Olivine and lesser magnetite have cumulus textures and are surrounded by anhedral plagioclase and pyroxene. Occurs as dikes and plugs cutting Tyler Formation. Generally massive with well-preserved igneous textures. Most pyroxenes have been converted to actinolite, hornblende, and biotite.