United States

Gilmore Expansion Mine

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Mine TypeOpen Pit
  • Gold
Mining Method
  • Truck & Shovel / Loader
Mine Life6 years (as of Jan 1, 2018)
ShapshotThe Fort Knox Gilmore project continues to progress on schedule and on budget, with initial Gilmore ore encountered in the fourth quarter of 2019 and stacked on the existing Walter Creek heap leach pad. Stripping advanced as planned during the quarter and is expected to continue throughout 2020. Completion of the new Barnes Creek heap leach pad, where 95% of Gilmore ore is expected to be stacked, and related pumping and piping infrastructure, remains on target for completion in the fourth quarter of 2020.

First gold ounces were poured from the new Barnes Creek heap leach pad in January 2021, which is part of the Gilmore project.


Kinross Gold Corp. 100 % Indirect
Fairbanks Gold Mining, Inc 100 % Direct

Deposit type

  • Mesothermal
  • Vein / narrow vein


Gold mineralization at Fort Knox Mine is hosted entirely within the Late Cretaceous (~92 Ma), Fort Knox granite pluton. The contact with the Fairbanks Schist is abrupt. Drilling indicates that the pluton contacts plunge steeply to the north and south and moderately to the east and west. The surface exposure of the pluton is approximately 1,100 m (3,609 ft) in the east-west direction and 600 m (1,969 ft) northsouth.

The Fort Knox Pluton has been subdivided into three phases based on grain-size and textural differences. Intrusion of a biotite-rich fine-grained granodiorite was followed by medium- grained porphyritic granite. The youngest intrusive phase is coarse-grained, porphyritic granite (Bakke, 1995). The texture is dominantly porphyritic, with megacrysts of quartz and k- feldspar, which become more sporadic in the fine- grained phase. The pluton is granite-granodiorite in composition, and the mineralogy of all phases is generally sub-equal amounts of quartz (30%), plagioclase (30-40%), and k-feldspar (20 to 30%) (Bakke, 1995; Blum, 1983).

The major structural trends controlling shear vein orientation and mineralization at the deposit- scale are defined by NW-trending, moderately to shallowly SW-dipping fault zones. The fault zones are typically filled with granulated white quartz, and range in thickness from 0.3 to 1.5 m. The zones have mixed groundmass alteration, with a range of phyllic and argillic alteration assemblages. In the vicinity of the fault zones, vein abundance increases and vein orientations are predominantly sub-parallel to the fault direction. The Monte Cristo Fault and Melba Fault zones are regional in extent and offset the Gilmore Dome Pluton south of Fort Knox and affect the orientation and geometry of the Fort Knox granite.

Gold occurs within and along the margins of pegmatite vein swarms and quartz veins and veinlets. Numerous SW-dipping fault zones influence the orientation of the vein swarms and the geometry of ore zones. Weak to moderate development of vein- andfracture-controlled phyllic, potassic, albitic, and argillic alteration styles is present. Gold is closely associated with bismuth (Bakke, 1995; McCoy et al., 1997). Gold occurs attached to bismuth- minerals, sulfide, and non-sulfide gangue, and as complex intergrowth or solid solution/exsolution texture grains with native bismuth, maldonite, bismuthinite, and/or molybdenite.

The overall sulfide content of the orebody is <0.10%. The orebody is oxidized to the depths of the drilling primarily along NW-trending, SW-dipping fault zones which contain abundant iron oxide and clay gouge along the margins.

Vein-types and associated alteration styles by abundance and relative importance to gold mineralization found at Fort Knox are:

1. Stockwork quartz veins and veinlets, ranging in thickness from micro-scale to 15 cm. These veins possess thin albitic alteration halos. Phyllic alteration envelopes that range in thickness from centimetre to multi-metre scale occur where stockwork veining is abundant near NW fault zones.

2. Pegmatite veins and veinlets: ranging in thickness from micro-scale to 8 cm. Composed of clear to grey quartz, large K-spar megacrysts, and micaceous clots. Potassic alteration halos, rarely exceeding 1 cm thickness, consist of an assemblage of variable amounts of secondary biotite and K- spar overgrowths on primary K-spar within the granite matrix. Veins variably altered with phyllic (quartz-sericite-pyrite) assemblage.

3. Low temperature fracture coatings and chalcedonic veins and breccia composed of zeolite- calcite-clay-chalcedony. Pervasive throughout the deposit in the form of fracture coatings and breccia zones. Argillic alteration halos as much as 7 m in width are developed adjacent to the larger chalcedonic breccia zones. These zones have been largely mined out to-date.

The Fort Knox deposit is classified as an Intrusion-Hosted Mesozonal deposit in the Reduced Intrusion-Related Gold Deposit (RIRG) style (Hart, 2005)



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Mining Methods


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Crushers and Mills

Milling equipment has not been reported.


Fort Knox currently operates two ore processing lines: a mill operation consisting of crushing, grinding, gravity concentration, agitated cyanide leaching, and a carbon-inpulp (CIP) circuit; and a run-of-mine valley-fill cyanide heap leaching operation where gold is recovered using two parallel carbon-in-column (CIC) circuits. In the near future, an additional valley-fill heap leach pad will be constructed and operated in series with the existing heap leach pad. Gold is recovered from solution by electrowinning and poured into doré bars at the mill refinery. The mill CIL processing facility is planned for closure in 2020, after which Fort Knox will become a 100% heap leaching operation. In post mill closure stage, it is planned that all ore materials will be directly processed without the use of stockpiles. All existing ore stockpiles at Fort Knox are scheduled for placement on the leaching facilities before the completion of mining, and as such there is no planned period of stockpile processing at the end of the mine life.



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CommodityUnitsLOM (Projected)
Gold M oz 1.5
All production numbers are expressed as metal in doré.

Production Costs

Commodity production costs have not been reported.

Heavy Mobile Equipment

Fleet data has not been reported.


Mine Management

Source Source
Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Oct 27, 2021
....................... Subscription required ....................... Subscription required Subscription required Oct 27, 2021
....................... Subscription required ....................... Subscription required Subscription required Oct 27, 2021
....................... Subscription required ....................... Subscription required Subscription required Oct 27, 2021

Aerial view:


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