Pyrite-rich ore bodies in tactite peripheral to a granitic stock were mined for their gold content at the Nabesna mine. The initial discovery was made in 1925 where a bear dug a hole that exposed the Bear vein that was to become the principal ore body in the mine (Wayland, 1943). A mill was in operation by 1931 and several ore bodies were developed over six levels of underground workings. There were 368 feet of surface cuts, 9,224 feet of drifts, and 6,209 feet of raises, in 650 vertical feet of mine workings (Wayland, 1943). Year-round operations were underway by 1935 when 60 tons per day were being milled. Most of the known ore bodies were mined out by 1939; total production was about 53,400 ounces of gold assuming a gold price of $35.00 per ounce. This recovery was from 72,994 tons of ore that varied in grade from 0.46 to 2.58 ounces of gold per ton. The ore had a weighted average grade of 0.93 ounce of gold per ton; 15,228 tons of tailings had a weighted average grade of 0.39 ounce of gold per ton (Wayland, 1943, p. 194). The average recovery for the life of the mine was 73 percent. The ore concentrate was shipped to the Tacoma smelter and some copper and silver credits were obtained.

The gold-rich ore bodies were discontinuous sulfide veins and replacements along marble-front contacts and crosscutting fissures (Wayland, 1943; Newberry and others, 1997). Pyrite was the most common sulfide but it was accompanied by lesser amounts of sphalerite, galena, and chalcopyrite, especially in upper parts of the mine. Arsenopyrite and stibnite were also reported and magnetite occurs locally at the margins or within some ore bodies. Sphalerite and galena occur in pockets and stringers cutting pyrite and along the edge of pyrite stringers, whereas chalcopyrite tends to be disseminated through the pyrite. Gold was with or near the later sulfides including chalcopyrite and galena. The principal gangue minerals are coarsely crystalline calcite and quartz. Oxidation extends a few tens of feet to as much as 350 feet below the surface; anglesite, cerussite, and a little sulfur were identified in oxidized portions of the veins (Pilgrim, 1931, p. 60-62; Wayland, 1943).

The individual ore bodies range in thickness from a few inches to 35 feet and average 5 to 7 feet thick. The Bear vein extends 320 feet horizontally, 250 feet vertically, and has a maximum thickness of 35 feet. The 'No. 49 stope' vein had a maximum horizontal length of 250 feet, a vertical length of 320 feet, and an average width of 4 to 5 feet. Other ore bodies were smaller irregular, pipelike, or tabular deposits. With the exception of the galena-rich 'No. 49 stope' vein, the ore bodies at lower levels had lower gold values, erratic mineralization, irregular shapes, and lesser amounts of sphalerite, chalcopyrite, and galena (Wayland, 1943). A five-foot sample across the Bear vein assayed 10.39 ounces of gold per ton 12.70 ounces of silver per ton, 1.67 percent lead, and 0.15 percent copper. A five-foot sample along the limestone/intrusive contact assayed 0.10 ounce gold per ton, 1.8 ounce silver per ton, and 4.2 percent copper (Pilgrim, 1931).