The deposit is a tabular shoot that follows a shear zone in massive acidic tuffs and gabbro. These host rocks have been intruded on a large scale by peridotite, now altered to serpentine and talc rocks. The ore, consisting of pyrrhotite, pentlandite, pyrite, and minor chalcopyrite, was emplaced in two separate injections. Temperatures determined from the composition of pyrrhotite in equilibrium with pyrite indicate a crystallization range of 530 degrees -490 degrees C for silicate-sulfide liquid and 530 degrees -400 degrees C for nearly pure sulfide liquid. Lowest temperatures were found in the central portion of the mass where the ores are thickest.