Customer Spotlight – Ft. Knox Gold Mine

The Fort Knox Gold Mine is located 40 kilometers by road from the city of Fairbanks, Alaska. The Fairbanks mining district is a northeast trending belt of lode and placer gold deposits that comprise one of the largest gold producing areas in the state of Alaska.

The Fort Knox area was actively explored for gold placer deposits since 1902 when Felix Pedro discovered gold in Fish Creek located downstream of the Fort Knox deposit. Since the initial discovery of gold in Fish Creek, the surrounding area has produced over 8 million ounces of gold predominantly from placer deposits many of which continue to operate to this day.

Construction of the Fort Knox Mine began in 1995 and was completed in 1997 at a cost of $373 million. Gold at Fort Knox occurs in and along the margins of quartz veins and veinlets and within fractures in the granite. Individual gold grains are generally less than 100 microns in size. Fort Knox ore is processed in a modern carbon-in-pulp extraction plant at a rate of upto 45,000T/day.

As indicated in the schematic flowsheet below, mill feed material is crushed to minus 20 centrimetres and conveyed to a coarse ore stockpile and subsequently to a semi-autogenous (SAG) mill that operates in closed circuit with two ball mills and a bank of cyclones for classification. A portion of the cyclone underflow (<10%) is screened and fed to two Knelson KC-XD48 Concentrators that account for ~10-15% of overall plant recovery much of it being the coarse slower leaching particles that can be adversely affected by the cold weather Alaskan climate which can significantly affect leach kinetics. In these conditions, the benefits of gravity are quite significant and the justification for installing a circuit is relatively straightforward and economically compelling.

Click here to link to full paper