From abstract: The nickel-copper deposit near the north end of Admiralty Island, about 18 miles in an airline west of Juneau, in southeastern Alaska, consists of a basic sill which averages somewhat more than 100 feet in thickness. The sill, which dips eastward, is intrusive into a thick sequence of phyllite and various types of schist. The rock of the sill consists principally of the silicate minerals labradorite and olivine, but it also contains magnetite and the sulfides pyrrhotite, pentlandite, and chalcopyrite. It assays, on the average, about 0.34 percent nickel and 0.35 copper, which are doubtless mostly in the pentlandite and chalcopyrite respectively but are probably constituents of other minerals also. A significant proportion of nickel and copper is probably contained in the olivine and perhaps in the pyrrhotite.