Most volcanic rocks of Mount Berlin define a trachyte suite, which features both comendite and pantellerite. Phonolite is less common. Mafic rocks have been reported from flank vents, basanite and hawaiite from Mefford Knoll, benmoreite from the southeastern flank at Wedemeyer Rocks, phonotephrite from Brandenberger Bluff and mugearite without any particular locality.