The project is located in the Battle Mountain-Eureka mineral belt in a large window of lower-plate carbonate rocks surrounded by upper-plate rocks. The area where the project is located has “Carlin-Type” sediment-hosted gold mineralization characteristics with typical associated alteration (decalcification, silicification).

Within the Gold Bar North (GBN) area, three gold deposits have been defined: Gold Pick, Gold Ridge and Cabin Creek. Mineralization in Gold Pick has a strike length of over 4,000 ft with a width of 1,600 ft and thickness of 100 – 150 ft. Gold Ridge and Cabin Creek are ancillary deposits comprising together approximately 22% of the mineral resource. All defined mineralization lies within 500 ft of surface in oxidized carbonate host rocks

Primary pyrite/marcasite and arsenopyrite generally replace iron-bearing minerals and form disseminations in unoxidized host rocks; they are generally fine grained and 1 mm to 1 micron in size. Late botryoidal pyrite/marcasite is present in some deposits. Most orpiment, realgar, stibnite, cinnabar, and barite are found in open space along fractures and in breccias.

Supergene minerals include travertine, goethite, limonite, hematite, alunite, kaolinite, stibiconite, scorodite, gypsum, celestite, and phosphate minerals. Small amounts of melanterite precipitate where ground water has evaporated from mined faces of unoxidized rock in open pits.

These deposits exhibit a characteristic suite of trace elements, including silver, arsenic, antimony, mercury, thallium, and barium ± tungsten ± selenium, whose abundances are elevated.

Gold mineralization at Gold Bar South (GBS) was deposited in brecciated siltstones of the Webb Formation, at and immediately above its underlying contact with the Devils Gate Limestone. Lesser but important amounts of mineralization occur in the adjacent Devils Gate Limestone as well. Mineralization in GBS consists of epithermal, disseminated, sediment-hosted gold, in zones related to hydrothermal dissolution in limestone and the resulting collapse breccia in the overlying siliciclastic unit. Gold is associated with brecciated, oxidized, silicified, and argillized mudstones, siltstones, and sandstones of the Webb Formation and is usually accompanied by silicification and strong barite veining. Jasperoid along the trace of the fault is brecciated and contains veins of barite and scattered gold mineralization. In contrast to the sediment-hosted GBN deposits, GBS gold mineralization is associated with brecciation. All known mineralization at GBS is oxidized and amendable to heap leach extraction.

Mineralization in GBS consists of epithermal, disseminated, sediment-hosted gold, in zones related to hydrothermal dissolution in limestone and the resulting collapse breccia in the overlying siliciclastic unit. Gold is associated with brecciated, oxidized, silicified, and clay-altered mudstones, siltstones, and sandstones of the Webb Fm and is usually accompanied by silicification and strong barite veining. The deposit exhibits a characteristic suite of Carlin- style trace elements, including arsenic, antimony, mercury, thallium, and barium ± tungsten ± selenium, whose abundances are elevated. The entire drilled extent of GBS, to a depth locally of over 800 ft, is oxidized to a mix of hematite and goethite.

The Gold Bar Project is planned for production using conventional hard rock open pit mining methods. Ore production to the plant is planned at 2,750 ktons/yr for the mine life. The mine production schedule was developed with the goal of filling the plant at required ore rate and maximizing the project return on investment. The total material rate is tied to equipment productivity and amounts to a maximum production rate of 39,700 tpd (14,500 ktons/yr). The mine is scheduled to operate 365 days/yr with two 12-hour shifts/day.

The Gold Bar Project is planned to be mined by a contractor. Contractor equipment on hand is often variable. There is flexibility in the fleet size and the actual mining fleet will likely vary depending on the contractor’s fleet on hand. The schedule and production requirements were based on 20 ft benches and the following fleet assumptions:

Drilling will be completed with a dual sized drill fleet.
Most of the waste is planned to be drilled with two rotary blast hole rigs with 60,000 lb pull down capacity and 6.75 in diameter blast holes.
The ore zones are planned to be drilled with two percussion drills sized with a 3.5 in diameter blast hole.

The blasted rock will be loaded into 100-ton haul trucks using three 15 cu yd front end loaders.

Precious metal recovery is through conventional heap leaching and adsorption, desorption, regeneration (ADR) technology for metal extraction from crushed and agglomerated ore. Processing will involve ore passing through a single stage of crushing, which will allow for belt conveyor stacking of the ore onto a heap leach pad. The processing facilities accommodate a leachable reserve of approximately 16.5 Mt of ore at a gold grade of 0.029 oz/t and a process rate of 8,057 tpd. The new heap leach pad has been located and designed with expandability for an ore reserve increase.

Over the life of the mine, ore will be delivered to the heap leach pad from each of the four open pits and placed in the stockpile adjacent to the crushing plant. The ore will be fed to the crushing plant using a front-end loader, and will be crushed, agglomerated with cement, and transported to the heap leach pad via an overland conveyor. The ore will be stacked onto the heap using a radial stacker and then leached with a weak cyanide solution to extract the precious metal values. The gold will then be recovered from the pregnant solution in the carbon plant by adsorbing the dissolved gold onto activated carbon followed by desorption, electrowinning, retorting and smelting to recover the gold as a final doré product.

A carbon ADR circuit will be used at the Gold Bar Mine to recover gold and silver from the pregnant solution. The ADR plant will recover and send concentrated gold solution to the refinery where the final marketable doré bars are produced. Pregnant solution from the heap leach pad will flow by gravity to the pregnant solution tanks. From the pregnant solution tanks, the solution will be pumped to the ADR plant, where soluble gold and silver will adsorb onto activated carbon. Adsorption of the gold onto activated granular coconut shell carbon will be conducted in a five-stage counter current carbon-in-column (CIC) circuit. Carbon is advanced from column to column counter current to the pregnant solution flow so that the highest-grade carbon contacts the highest grade pregnant solution and the most active fresh carbon contacts the lowest grade solution.

Loaded carbon from the first adsorption column will be pumped to an acid wash vessel and will be acid washed by circulating dilute nitric acid upwards through the bed of carbon to remove scale build-up (mainly calcium) to maintain the carbon’s ability to recover gold and expose the surface to improve gold elution efficiency. Residual acid in the acid wash vessel will be neutralized with caustic before the loaded carbon is transferred to the strip (elution) vessel. Hot caustic cyanide solution will be pumped through the strip vessel to remove the gold and silver from the loaded carbon. Elution is conducted at 100 psi and 300°F for up to ten hours. Sodium hydroxide will be added to the stripping solution to aid stripping and provide electrolyte for the subsequent electrowinning stage.

Stripped carbon will be transferred to the regeneration circuit where carbon will be thermally regenerated in a horizontal rotary kiln or the carbon may be sent directly to the sizing circuit and returned to the carbon columns. Stripped carbon will be washed with water then screened to remove fines prior to being fed to the regeneration kiln. There it is heated to approximately 1,200 to 1,400°F in a moist, oxygen- free atmosphere to reactivate its surfaces before it is reused in the carbon columns.

Recovery of precious metals from the rich pregnant strip solution will be conducted in a single electrowinning (EW) cell. Electrowinning removes the precious metals from the pregnant solution by passing direct current through an electrowinning cell. The rich strip solution is transferred to the electrowinning cells. The precious metal ions transfer from the solution to the stainless-steel wool cathode and deposit onto the steel wool as a weakly bonded sludge. The barren EW solution is then returned to the stripping circuit, completing the elution cycle. The barren strip solution from the electrowinning cell will be collected in the EW barren return tank and pumped to the strip solution tank for reuse in the strip circuit. The sludge in the electrowinning cell will be washed off the cathodes in batches and recovered as a damp cake in the cathode sludge filter press.

The filtered cake will be retorted to remove and recover mercury prior to smelting the dried sludge to produce Doré bars. Filtered cake will be collected in pans. The pans will be placed in a mercury retort system for several hours. The retort will heat the filtered cake to approximately 1,100°F to vaporize mercury. The retort temperature will be ramped up gradually to enable the sludge to dry completely before mercury is vaporized and to allow time for the mercury to diffuse to the solid surfaces. Retort vapor will be withdrawn from the retort by a vacuum pump, which will pull the vapor through a condenser where the mercury will condense and flow into a mercury collection compartment. Mercury will be removed as required.

Following a cooldown period, the dried (retorted) cake will be mixed with fluxes and charged to an electric induction furnace and heated to approximately 2,250°F. When the furnace charge is fully molten, it separates into two distinct layers: the slag (on the top) and metal (on the bottom). The slag layer, containing fused fluxes and impurities, will be poured first into conical pots. Once slag has been removed, the melted gold and silver (metal layer) will be poured into molds to form Doré bars.

Bars will be cooled, cleaned, weighed, and stamped with an identification number and weight. Doré bars will be the final product of the plant which will be shipped to the market at 90-95% Au/Ag purity.