The Keno Hill Mining camp has long been recognized as a polymetallic silver-lead-zinc vein district with characteristics possibly similar to other well known mining districts in the world. Examples of this type of mineralization include the Kokanee Range (Slocan), BC; Coeur d’Alene, Idaho; Freiberg and the Harz Mountains, Germany; and Príbram, Czech Republic.

The common characteristics of these locales are the proximity to crustal-scale faults, the occurrence in a package of monotonous clastic metasedimentary rocks, which have been intruded by plutons. Even though the mineralization is not likely related to the intrusions, they may have acted as a heat source for hydrothermal circulation. Mineral precipitation occurred where metal-laden hydrothermal fluids with a temperature of 250°C to 300°C travelled through open fractures caused by a local tensional stress regime in an otherwise compressional environment and precipitated metals as pressure and temperature changed.

The Bellekeno vein system consists of numerous veins with variable strike, dip, and thickness. The main mineralized structure, the 48 vein-fault occurs in three distinct mineralized zones: Southwest, 99, and East with the bulk of historical mining occurring in the 99 Zone. The average strike is approximately 030° azimuth with an average dip of 60° to 80° to the east or west. Reported thickness ranges from just a few centimetres to several metres. Faults, originally exposed underground, show intense iron carbonate alteration and local brecciation. Mineralized zones are largely composed of siderite and limonite. Ore minerals include freibergite and galena, and sphalerite. Accessory minerals are anglesite, cerrussite, smithsonite, malachite, arsenopyrite, pyrite, chalcopyrite, and azurite.

Access to the underground workings at Bellekeno combined with the significant increase in drill hole data in 2009 led to a more comprehensive understanding of the mineralization controls. An updated structural and stratigraphic interpretation of the Bellekeno mine area and their effects on the 48 vein/fault (Otto, 2009).

The Bellekeno 48 vein lies in the damage zone of the curviplanar 48 vein/fault. The fault meanders along strike and dip, and the mineralized parts (ore shoots) are restricted to specific segments defined in part by strike orientation and dip steepness.

When Alexco resumed mining at the Bellekeno mine in 2010, the majority of the vein material was mined by overhand mechanized cut and fill (MCF) methods. Each lift of MCF was typically accessed from the footwall ramp system by a 3.5 m wide by 3.5 m high attack ramp. Depending on the grade and length of the attack ramp, 3 to 4 additional cuts of MCF were economically accessed. To do this, a section of back in the crosscut or attack ramp was slashed down and then rebolted. The broken waste rock from the take down back (TDB) slashes was left in place and graded to access the next cut.

Alexco began trials of a small scale longitudinal retreat longhole mining method in 2012 and has been reasonably successful in applying this method to both the SW and 99 zones at Bellekeno. The intent is to mine a large portion of the mineral resources remaining in the SW and 99 zones using this method.

The mill facility consists of a two-stage closed circuit crushing line (jaw crusher followed by cone crusher), feeding the fine material stockpile. The single-stage grinding circuit has a ball mill (1.8 x 3.6 m, 180 kW) in closed circuit with a 300 µm vibrating screen to produce a mill feed P80 size of 174 µm. The screen undersize feeds the lead rougher/scavenger flotation circuit to recover lead and silver minerals to a rougher concentrate and scavenger concentrate.

Rougher and scavenger silver-lead flotation concentrates feed a three-stage lead cleaner flotation circuit generating a final silver-lead concentrate. The lead scavenger tailings feed the zinc rougher scavenger flotation circuit to recover the zinc minerals generating the final, low pyrite tailings, which are stored in a dry stacking facility.

The zinc rougher flotation concentrate feeds a three-stage cleaner flotation circuit, which produces the final zinc concentrate and a high pyrite tailing. The silver-lead concentrate and the zinc concentrate are thickened and filtered prior to transport off site. The high pyrite tailings are thickened and used for underground backfill. Regrinding of either lead or zinc rougher concentrates is currently not included in the mill facility flowsheet.