The DDX zone of massive sulfides crops out in a creek; one layer of mineralization 10 to 20 inches thick is exposed, as are several thinner bands 1 to 2 inches thick. The thicker layer is a banded massive sulfide dominated by pyrite; it has more chalcopyrite at its base and more sphalerite and galena at its top. The mineralization occurs within a 15-foot-thick black carbonaceous phyllite enclosed by felsic metavolcanic schist. The massive sulfide is exposed for about 30 feet before it lenses out or is covered by talus (R.A. Blakestad and others, unpublished Resource Associates of Alaska, Inc. report, 1978). Samples from the DDX exposure average 0.5 percent copper, 3.3 percent lead, 5.5 percent zinc, 54 parts per million (ppm) silver, and 0.1 ppm gold (Dashevsky and others, 2003).The DDX occurrence occupies the same mineralized unit or layer as the DD North prospect (MH319); it is along the upper contact of the Drum felsic unit and beneath the Tok River sequence. The Tok River unit is a thick assemblage of metasedimentary rocks that consist of chloritic phyllites, quartz-sericite (-chlorite) schist, phyllitic quartz-eye metagrits, carbonaceous phyllite, and minor marble. Some of the metagrits contain feldspathic detritus and are locally calcareous. The protolith of the Tok River unit is about three-quarters sedimentary and one-quarter volcanic. It has minor interbeds of felsic volcanic rocks similar to the rhyolite and rhyodacite of the Drum unit (Dashevsky and others, 2003).