The Gibraltar open pit mine is a calc-alkalic porphyry copper-molybdenum deposit entirely hosted by the Late Triassic Granite Mountain batholith.

Primary hypogene copper mineralization in the form of disseminated and vein-hosted chalcopyrite predominates at Gibraltar. Minor bornite occurs typically in the east and northeast portions of the deposit. Molybdenite occurs mainly in quartz veins and fractures, and rarely as matrix disseminations. Sphalerite occurs in the Extension deposit, and is especially abundant in the TK Zinc zone farther west. Mineralization in the Granite, Pollyanna, and Connector deposits is hosted in massive to strongly foliated zones. In contrast, mineralization in the Gibraltar, Extension, and TK Zinc zones is almost entirely hosted in strongly foliated shear zones.

Pyrite and chalcopyrite are the principal primary sulphide minerals of the Gibraltar deposits. Fine-grained chalcopyrite, generally barely visible without magnification, accounts for 60 percent of the copper content and constitutes the single most important form of copper mineralization. Most of this fine fraction is dispersed within the phyllosilicate foliation lamellae and forms the uniformly distributed grades of the Gibraltar porphyry-type ores. Coarser grained chalcopyrite usually occurs in quartz veins and shear zones. Pyrite mineralization generally shows some degree of segregation from chalcopyrite and, in the Pollyanna and Granite deposits, pyrite forms a halo or blanket of waste material above and away from the orebody. Large-scale pyrite zoning is also evident in the Gibraltar deposit but without the formation of a separate halo. The Connector zone displays mineralization features similar to both the Gibraltar and Pollyanna deposits. In the Gibraltar and Extension, pyrite is closely associated with the ore, often as massive zones 3 m to 7 m thick.

Small concentrations of other sulphides are present in the Gibraltar ores. Bornite, associated with magnetite and chalcopyrite, occurs along the low sulphur extremities of the Pollyanna deposit. Molybdenite is a minor but economically important associate of chalcopyrite in the Pollyanna, Granite, and Connector deposits. Small zones of molybdenum mineralization as molybdenite also occur in Gibraltar but are virtually absent in the Extension. Sphalerite is present in the Gibraltar deposit and particularly abundant in parts of the Extension. Both of these deposits also have elevated silver concentrations associated with copper mineralization. The above relationships suggest a metal zonation from Pollyanna to the Extension Zone that involves a westerly decrease of molybdenum and a corresponding increase of zinc and silver. Overall, in terms of large-scale metal zonation Gibraltar ranges from Cu±Mo in the east to Cu±Zn towards the west.

There is a close spatial relationship between sulphide mineralization and alteration in the Gibraltar deposits. The principal alteration minerals are chlorite, sericite, epidote, carbonate and quartz. Ore grade mineralization is associated mainly with sericite and chlorite. Epidote and the carbonate minerals are not common associates of strong sulphide mineralization. Quartz is common throughout the alteration sequence as both a relict host rock mineral and an introduced mineral.

Supergene mineralization and secondary enrichment occurs to varying degrees in the Gibraltar and Connector deposits and is interpreted to be a remnant of a pre- or inter-glacial period of weathering (Bysouth et al., 1995). Supergene enrichment is best developed in close association with pyrite-rich ore (> 3% pyrite). Supergene enrichment occurs directly beneath a leach cap, forming a blanket-like zone about 15 m to 30 m thick containing the supergene copper minerals chalcocite, digenite and covellite. Episodes of Pleistocene glaciation removed most of the Tertiary weathering surface elsewhere. The present zone of oxidation and leaching in other areas is generally confined to the upper 1 m to 3 m of the bedrock surface. Limited zones of oxidation may also occur to depths up to 100 m where structural controls have facilitated significant groundwater percolation.

The Gibraltar deposits have been developed using open pit, truck and shovel mining methods since 1971. To date (March 2022), mining has progressed in several phases in the Gibraltar, Pollyanna, and Granite pits with future mining to continue in the Pollyanna and Gibraltar pits as well as the undeveloped Connector and Extension pit areas.

Mining operations supply 85,000 tons per day of ore at an average head-grade of 0.25% copper to two primary crushers which in-turn feed the two concentrators. During the 23-year mine life, a total of 699 million tons of sulphide ore, 17 million tons of oxide ore and 1,667 million tons of waste will be mined from the reserve pits at a strip ratio of 2.4. An additional 6 million tons of stockpiled ore will be processed.

For strategic and operational reasons surplus ore is stockpiled at various times during the mine life and for various amounts of time prior to processing. Waste rock is stored in various waste rock storage facilities next to the pits, as well as in previously mined pits after mining of those pits is complete. Suitable overburden waste is salvaged and stored separately for use in reclamation.

Pit Design
All the pits in the reserve plan are designed with a bench height of 50 ft, a bench face angle of 65 degrees. Safety berms are a minimum of 27 ft wide and are increased to achieve inter-ramp wall angles presented in Section 15 of this report. Haul ramps or 60 ft wide geotechnical safety berms are included every 350 vertical feet or 7 benches are included to provide additional catchment and break up large pit walls.

Haul roads are designed 120 ft wide to allow for double-lane haulage with allowances for berms and ditches. Single-lane, 90 ft wide roads are used to maximize ore extraction and mining width at pit bottoms. Road grades are limited to 10% with flat switchbacks.

Production Schedule
The reserve mine plan begins with mining already underway in the Pollyanna and Gibraltar pits. In 2023 mining will begin in the Connector pit, and in the following year activity in the Gibraltar Pit will cease temporarily. In 2025, mining in the Pollyanna pit will also cease temporarily. Connector pit will be the sole focus of mining activity from 2026 until 2028 when mining of the Gibraltar pit will restart. The Connector pit will be exhausted in 2031 and the Gibraltar pit will continue to be mined until 2038. The Extension pit and the remainder of the Pollyanna pit will be mined from 2036 to 2040 and 2040 to 2044 respectively.

The average mining rate over the operating life is 104 million tons per year. Sulphide ore moved (including stockpile rehandle) averages 33 million tons per year. Oxide ore is mined sporadically throughout the schedule with 90% of the total 17 million tons coming from the Connector Pit between 2024 and 2027.

Bulk Concentrator #1
Gibraltar sulphide ore is processed through a single stage of crushing using a 60x89 gyratory crusher. This crusher produces a 6 inch minus product which is conveyed to a coarse ore stockpile. Material is drawn from the coarse ore stockpile using apron feeders and a conveyor belt to feed a 34 foot diameter, 13,000 Hp Semi-Autogeneous Grinding (SAG) mill. SAG mill discharge is screened with the oversize returning via conveyor belt to the feed of the mill. Undersize material, consisting of 0.5 inch minus, is then pumped to a distributor where six 13.5 foot diameter, 2500 Hp ball mills are operated in closed circuit with hydrocyclones to produce a minus 350 micron product used to feed the flotation circuit. Design mill throughput is 55,000 t/day.

Bulk Concentrator #2
Gibraltar sulphide ore is processed through a single stage of crushing using a 54x74 gyratory crusher. This crusher produces a 6 inch minus product which is conveyed to a coarse ore stockpile. Material is drawn from the coarse ore stockpile using apron feeders and a conveyor belt to feed a 34 foot diameter, 13,000 Hp Semi-Autogeneous Grinding (SAG) mill. SAG mill discharge is screened with the oversize returning via conveyor belt to the feed of the mill. Undersize material, consisting of 0.5 inch minus, is then pumped to a distributor where a single 20 foot diameter 8,500 Hp ball mill is operated in closed circuit with hydrocyclones to produce a minus 350 micron product used to feed the flotation circuit. Design mill throughput is 30,000 t/day.

Sulphide ore is processed at a design rate of 85,000 t/day through two bulk concentrators to produce a concentrate which contains copper, silver and molybdenum values. The bulk concentrate from both facilities is combined and processed through a single molybdenum flotation plant. The molybdenum concentrate from this plant is dewatered and bagged, and subsequently shipped to market. The underflow from this plant is the final copper concentrate which includes silver as a by- product. The copper concentrate is dewatered and shipped in bulk to market.

A solvent extraction and electrowinning plant processes leachate from oxide waste dumps to produce a copper cathode product. This system is operated intermittently as conditions allow.

Bulk Concentrator #1
Flotation feed is pumped to two parallel rougher flotation circuits, each consisting of five 160m3 flotation vessels. Flotation tailings are then pumped to a storage facility. Rougher concentrate from the parallel ........