In 1987, as part of an Alaska critical and strategic minerals project, the Bureau of Mines evaluated an occurrence of tin and lead- silver mineralization in the Cosna River drainage near the Bitzshtini Mountains. Tin mineralization is found in dense gossan associated with concentrated quartz veining distributed along linear depressions bearing 140 deg. Across a thinly vegetated dome. Gossan grades to 2 to 3 pct sn with anomalous levels of ag, pb, zn, sb, and as. Lead-silver mineralization (average 71 pct pb, 91.3 Oz/ton ag) occurs nearby as podlike masses of galena associated with <1-ft-wide vuggy quartz veins with easterly orientations. Stibnite mineralization is locally present in the lead-silver prospect. Heavy mineral sampling of stream drainages and geologic reconnaissance traverses established a widespread distribution of tourmaline and delineated isolated areas anomalous in sb, ree, ag, te, th, sn, w, u, and pb. Regional geology and available airborne magnetic and radiometric surveys suggest that mineralization reflects hydrothermal activity distal to a buried pluton which possibly cores a portion of the Bitzshtini Mountains several miles to the south of the study area.