In eastern Papua, the Papuan ultramafic belt lies on the northern side of the belt of Paleozoic? metamorphics that form the Owen Stanley range. The outcrops in the Musa valley represent the eastern extremity of the belt, with the exception of the ultramafics that occur at Milne bay. Subsequent volcanic activity after the emplacement of the belt, with penetration of country rock by volcanic gases has produced vent and extrusive breccias that are either irregularly shaped bodies or horizontal sheets. The breccias show several stability fields for the mineral assemblages, which are correlated with variation in the intensity of brecciation. The assemblages include chrysotile and lizardite, antigorite, olivine, and enstatite. Ten chemical analyses are given, five pairs representing matrix and fragment in five specimens. Origin and relation to the serpentinite problem are discussed.