The Rum North prospect is in a west-northwest-trending, steeply south dipping sequence of metavolcanic and metasedimentary rocks that have been intruded by gabbroic sills in the central and basal part of the Drum unit. The Rum North prospect is about 1,000 feet away from the Rum South prospect (MH343) and separated from it by an inferred fault (R.A. Blakestad and others, unpublished Resource Associates of Alaska Inc. report, 1978). The Drum unit that hosts the Rum prospects consists of white to pale gray-green, rusty weathering, quartz-sericite(-chlorite-pyrite) schist with minor gray to black carbonaceous phyllite and rare interbeds of chloritic phyllite. The schist commonly contains 1 to 5 percent quartz eyes but may contain more. The protoliths of the schist are about two-thirds of volcanic origin and one-third of sedimentary origin. The schist has a phyllitic parting in many places (Dashevsky and others, 2003).

The Rum North massive sulfide deposit is poorly exposed near the top of a steep talus-covered slope. A train of sparse sulfide float below it contains both copper-rich and lead-zinc-rich cobbles that suggest the presence of a strongly zoned sulfide horizon. Cobbles of massive sulfide found in Rum Creek are generally fairly small, rarely as large as 12 inches. The limited outcrop exposure shows two bands of massive sulfide, each less than 1 foot thick. Representative assays have 3.9 percent copper, 5.5 percent lead, 10.1 percent zinc, 20.5 parts per million (ppm) silver, and 0.2 ppm gold (Lange and others, 1993; S.S. Dashevsky, written communication, 2003).

Nine grab samples of massive sulfide from the Rum North and Rum South zones average 4.21 percent copper, 7.07 percent lead, 8.95 percent zinc, 2.89 ounces of silver per ton, and traces of gold. The highest grade samples contain 37.2 percent combined copper, lead, and zinc with as much as 11.7 ounces of silver per ton (J.K. Muntzert and others, unpublished Resource Associates of Alaska Inc. report, 1977).