Mineralization at the win prospect was investigated by the Bureau of Mines in June 1990 and 1991, as part of an ongoing investigation of the tin, niobium, and tantalum resource potential in Alaska. The win prospect is located 20 miles northwest of McGrath, Alaska. Mineral deposits consist of polymetallic sulfide and quartz-cassiterite mineralized vein and breccia vein systems within a quartz-tourmaline (dravite)-altered hornfels aureole that appears to be related to a small dacite stock and dikes. Host rocks for most of the veins are altered, late Cretaceous kuskokwim group flyschoid rocks. The dacite is a calc-alkalic, high-ca, low-k, biotite, magnetite, garnet- bearing coarse-grained intrusive. Mafic and accessory mineral distribution in the stock and dikes is highly erratic. Veins and breccia veins often contain high tin and silver values (as much as 18.82 Oz/st ag and 6.97 pct sn over 7.75 Ft), variable, but significant, amounts of copper, lead, zinc, arsenic, niobium, antimony, bismuth, and tellurium, and trace amounts of gold, indium, and selenium. Mineralization is both distal and proximal to the dacite intrusive rocks, covering a roughly circular area 1.25 Mile in diameter. Bedrock exposure of vein systems is limited and no resource is calculated.