Jerritt Canyon is a Carlin-type gold deposit, hydrothermal in origin and usually structurally controlled.

Jerritt Canyon is hosted by silty carbonate or carbonaceous siliciclastic rocks originally deposited as shelf sedimentary rocks during the Paleozoic age. The Paleozoic host rocks have been imbricated, faulted, and folded through several orogenic events in the Paleozoic and Mesozoic. An early phase of intrusive igneous activity is represented by west-northwest mafic igneous dikes of Paleozoic age.

In general terms, the intersection of structures with favourable host rocks is the primary control and the form of mineralization ranges from apparently stratabound to fault hosted where the faults can be either highly discordant to bedding or bedding-parallel. Deposits at Jerritt Canyon are mostly stratabound or fault hosted. Gold occurs as very fine, micron sized, particles in pyrite and arsenian pyrite. Other sulfides are orpiment, realgar, and stibnite. Alteration includes decarbonatization, decalcification, and silicification (jasperoid).

Gold mineralization at Jerritt Canyon is hosted by Hanson Creek Formation units and the lower part of the Roberts Mountains Formation. The Saval discontinuity, being the contact between the Hanson Creek and the Roberts Mountain Formations, is interpreted as a primary control on gold mineralization at Jerritt Canyon. Gold mineralization is hosted by, or spatially associated, with high angle west-northwest- and north-northeast-trending structures. Much of the more continuous gold mineralization occurs within the favourable stratigraphic intervals along the limbs or hinge zones of large anticlinal folds, and at the intersection of the two sets of high angle structures. The mineralized zones form along well defined structural and mineralization trends as stratigraphically controlled tabular pods that are locally stacked upon one another resulting from the presence of more than one favourable stratigraphic unit and/or local thrust and/or high angled fault intersection controls. The deposits are Carlin type, sediment-hosted gold mineralization within carbonaceous sediments. Gold occurs as very fine-grained micron-sized particles as grain boundaries or inclusions in pyrite, and as free grains in carbonaceous-rich and fine-grained, calcareous, clastic sedimentary rocks.

Alteration in the Jerritt Canyon district includes silicification, dolomitization, remobilization, and reconstitution of organic carbon, decalcification, argillization, and pyritization (typically containing elevated arsenic). The rocks also exhibit hypogene and supergene oxidation and bleaching. The most important alteration types relative to gold deposition are silicification, remobilization, and reconstitution of organic carbon, pyritization, and decalcification.

SSX
SSX mineralization occurs predominantly in the micritic unit III of the Hanson Creek Formation. A smaller portion of the mineralization occurs in calcareous siltstone at the base of the Roberts Mountains Formation or in the upper two cherty and dolomitic members of the Hanson Creek Formation. Mineralized zones are localized in and near west-northwest-trending steeply dipping dikes (e.g., South Boundary Dike); however, dike material is a minor component of the mineralized material at SSX. Mineralization is also localized along cross-cutting northeast-trending faults. Folding of the mineralized horizons is apparent along axes parallel to the west-northwest dike trend and, more prominently, parallel to the northeast fault set. Gold occurs in decarbonatized rock, commonly in association with variable amounts of orpiment and realgar. Silicification with stibnite can also be associated with gold in portions of the upper cherty member of the Hanson Creek Formation.

Gold mineralization in the Steer portion of the SSX complex has been identified in an area stretching approximately 3,000 ft east from the old Steer pit to halfway along the connection drift to SSX Zone 5. Most gold mineralization at Steer is associated with gently dipping structures cutting through Hanson Creek unit III. These structures strike northeast and dip southeast, offsetting strata. Zones of mineralization typically follow the structures and tend to be broad and relatively thin. The mineralized zones are usually at the contact between Hanson Creek Formation units III and IV and occasionally follow the structures up through unit III. Both within the Steer portion and the western side of SSX, several low angle features have been observed. These features are at least partly responsible for the gold mineralization at the contact of Hanson Creek Formation units III and IV.

In the eastern portion of the Steer area, high grade mineralization is associated with the Husky Fault, a major northeast trending normal fault with approximately 300 ft of normal dip-slip displacement to the southeast. Major northwest trending dikes appear to have locally compartmentalized high grade mineralization. The intersection of these dikes with Hanson Creek Formation unit III and the Husky Fault and its related structures offers excellent exploration potential. One of these dikes is interpreted to be the western extension of the South Boundary dike, which is an important ore-controlling structure at SSX to the east.

Smith Mine
The mineralization at Smith generally trends northwest with minor northeast trends along minor structures. Mineralization is continuous along the northwest trend ranging from 200 ft to 2,500 ft. The width of the mineralization ranges from 20 ft to 400 ft and the thickness ranges from 10 ft to 100 ft. The depth of the mineralization ranges from near surface at the Dash open pit to 1,200 ft below the surface to the south and east.

In Smith Zone 1, high-grade gold mineralization is hosted in the upper and middle portions of Hanson Creek Formation unit III within a northwest-trending horst block between the South Graben Fault and the 170 fault. Mineralization in Zones 2 and 3 is directly associated with west-northwest-trending dikes. Highgrade mineralization occurs within Hanson Creek Formation units II and III along the steeply dipping dikes. Lesser amounts of mineralization exist at higher levels where the dikes intersect favourable beds in the Roberts Mountains Formation. An exception to the tight elevation controls on mineralization is observed at the intersection of the west-northwest-trending dikes and the Coulee Fault. Here, high-grade mineralization blows out into Hanson Creek Formation unit III along the west plunging intersection of the dikes and the fault for a down-dip depth of 600 ft.

Jerritt Canyon has been in operation since 1981, with open pit operations occurring from 1981 to 1999, and underground operations commencing in 1993 at SSX and Smith. SSX and Smith are currently contractor operated.

SSX is accessed via ramp located in the southeast portion of the underground mine at the bottom of a historical open pit, and underground workings strike northwest to southeast, spanning approximately 10,000 ft. SSX is comprised of seven mining zones, with Zone 1 in the east and Zone 7 in the west. The zones overlap in areas due to overlapping orebodies in the vertical plane. SSX is ventilated via a series of raises and through the main ramps. Mineralized material is hauled from muck bays and stockpiled near the portal, where it is then delivered to the mill via larger haul trucks. All mining voids are filled with cemented rock fill (CRF).

Smith is accessed via a ramp located at the bottom of the inactive Dash open pit. Underground workings are extensive and access eight distinct mining zones, though only six zones have been considered by SLR in the estimation of Mineral Reserves. Smith is ventilated via a series of raises and through the main ramp. Similarly to operations at SSX, mineralized material is hauled from muck bays and stockpiled near the portal, where it is then delivered to the mill via larger haul trucks. All mining voids are filled with CRF.

Stoping Methods
Production at SSX and Smith utilizes the cut and fill stoping method. Minimum mining openings are 15 ft by 15 ft, with widths of up to 25 ft where justified by the mineralized structure width. Stopes are mined using a combination of overhand and underhand methods, with a stope typically consisting of three lifts. The middle lift is mined first, followed by the top lift to allow for curing of the first lift before mining of the bottom lift occurs. Ore is hauled to surface stockpiles using mine haul trucks for grade control and surface haul trucks to the mill feed stockpile. These methods have been employed successfully at Jerritt Canyon since underground operations began. Based on SLR’s site visit, SLR considers the mining methods to be adequately applied.

Mine Development
SSX and Smith are accessed by way of surface portals and 15 ft by 15 ft declines typically grading 12% to 15%. Underground lateral development including level and stope access is generally designed to be 15 ft by 15 ft. Cut and fill stopes are typically mined in three lifts with access drift gradients varying from +15% to -15%. All aspects of the mining cycle are fully mechanized with excavations created using conventional drill, blast, muck, and support techniques.

Backfill
Backfilling of production voids is completed using CRF, which is produced by crushing and screening mine waste material and placed using a load-haul-dump unit (LHD) with a rammer push plate attachment. Cement content varies from 5% to 6% for adjacent and undercut mining, with the majority of fill placed with 6% cement content. CRF is mixed at batch plants located near the portal of each mine and hauled underground by mine haul trucks. In cut and fill mines, CRF is loaded into cut and fill stopes using loaders and pushed tight to the back using a dozer or loader.

Primary Crushing
ROM mineralized material is crushed to minus six inches with a 36 in. by 42 in., 200 hp jaw crusher.

Fine Crushing
Dried mineralized material from the dryer is conveyed to the secondary crushing vibrating screen, a 5 ft by 12 ft double deck screen with ¾ in. top deck screen panels and ¼ in. bottom deck screen panels. Screen
oversize is fed to the 4.25 ft standard Omnicone crusher. Minus ¼ in. screen undersize by-passes the secondary crusher and is transported by screw conveyor and a standard conveyor belt to the high angle conveyor that joins the material on the fines conveyor from the crushing circuit. Fine material is transported to the 2,000 st capacity fine ore bin (FOB). Approximately 30% of the material discharging from the dryer discharge is minus ¼ in.

Ore from the secondary crusher is conveyed to the 100 st tertiary crusher feed bin, which has two discharge points that each feed a 6 ft x 16 ft double-deck vibrating screen. The top deck of the screens has ¾ in. openings and the bottom decks have ¼ in openings. Oversize from each screen is fed to a 4.25 ft short head Omnicone crusher. Minus ¼ in material by-passes the tertiary crushers and reports to fines conveyor that transports the material to a high angle conveyor that discharges to the FOB. Material stored in the FOB feeds the grinding circuit.

The fine crushing circuit is served by a north and a south baghouse. Fine material collected in the north baghouse is pneumatically conveyed to the roaster feed bin (RFB) by a puker system. The south baghouse has a FL Smidth Fuller-Kinyon pump to move fine material collected in the baghouse to the RFB.

Grinding
Ore from the FOB is conveyed to the 14.5 ft x 18.5ft ball mill. The grinding circuit was designed to reduce the mineralized material from 100% passing (P100) 1/4 in mineralized material to P100 35 mesh (i.e., 500 µm). The ball mill is driven by a 2,750 hp synchronous motor. The mixed ball charge is approximately 40% by volume. The makeup ball sizes are 2.5 in., 2.0 in., and 1.5 in. Mineralized material passes through the discharge grates to an air slide and then to a bucket product elevator that transfers the ground material to an Osepa air classifier. Classifier oversize reports back to the ball mill for further size reduction. The circulating load is approximately 300%.

Fines from the classifier oversize report to separator cyclones, where approximately 88% of the fines are removed from the air stream. The collected fines are deposited into the product bucket elevator feed air slide. The air stream, with the remaining 12% entrained fines, reports to the 700 hp, 131,000 actual cubic feet per minute (acfm) separator fan. 66% to 75% of this stream is fed back into the air classifier through the separator fan, while 25% to 33% of the stream is bled into the classifier baghouse.

The classifier baghouse uses the 125 hp classifier baghouse fan to pull 44,800 acfm of air through the bag filters. The captured dust is transported via an air slide and the 60 hp product bucket elevator to the RFB.

The processing facilities at Jerritt Canyon are designed to operate at a rate of 4,500 stpd with an operating availability of 90% and are permitted to operate at 6,000 stpd. The facilities include:
• Primary crushing?
• Ore drying;
• Secondary crushing;
• Tertiary crushing;
• Dry grinding;
• Roasting;
• Thickening;
• Carbon-in-leach (CIL);
• Carbon stripping;
• Carbon reactivation;
• Electrowinning;
• Electrowinning sludge refining;
• Oxygen plant;
• Cooling pond;
• Water evaporation pond;
• Tailings Impoundment.

Roaster
The roaster feed bucket elevator lifts the mixture of ore and pulverized coal approximately 135 ft and discharges into the roaster feed air slide. A disengaging bin receives the air slide discharge and funnels this material into the fluidized feed distributor. The roaster system is comprised of two identical, side by side roaster trains, each train is permit ........