The Cortez deposits are “Carlin” style sedimentary rock-hosted and porphyry/epithermal deposits. Carlin deposits form as structurally and/or stratigraphically controlled replacement bodies consisting of strata-bound, tabular, disseminated gold mineralization occurring in Silurian-Devonian carbonate rocks. Deposits are localized at contacts between contrasting lithologies, metamorphosed to varying extents. They can also be discordant or breccia-related. The deposits are hydrothermal in origin, are usually structurally controlled and at Cortez are hosted in Lower Plate carbonate strata exposed by two erosional windows through allochthonous Upper Plate siliclastic units; the windows are on either side of Crescent Valley.

Mineralization consists primarily of submicron to micrometre-sized gold particles, very fine sulphide grains, and gold in solid solution in pyrite. Gold is disseminated throughout the host rock matrix in zones of silicified and decarbonatized, argillized, silty calcareous rocks and associated jasperoids. Gold may occur around limonite pseudomorphs of authigenic pyrite and arsenopyrite. Major ore minerals include native gold, pyrite, arsenopyrite, stibnite, realgar, orpiment, cinnabar, fluorite, barite, and rare thallium minerals. Gangue minerals typically comprise fine-grained quartz, barite, clay minerals, carbonaceous matter, and late-stage calcite veins.

In the Cortez district, the favoured host rocks for gold mineralization are the Wenban Limestone, followed by the Horse Canyon and Roberts Mountain formations. Mineralization reflects an interplay between structural and lithological ore controls in which hydrothermal solutions from intrusives moved to favourable porous decalcified limestone. Mineralized host rocks are predominantly characterized as oxides, along with sulphidic and carbonaceous refractory material. Carbon content in the deposits is highly variable and occurs generally in the Wenban and Roberts Mountain Formations.

Supergene alteration extends up to 656 ft depth resulting in oxide ores which overlie the refractory sulphides. Alteration has liberated gold by the destruction of pyrite and resulted in the formation of oxide and secondary sulphate minerals which include goethite, hematite, jarosite, scorodite, alunite, and gypsum.

The Cortez Hills underground mine is accessed by twin declines portaled in the old Cortez Gold F canyon pit. The Pipeline and South Pipeline deposits are mined by conventional open-pit methods.

Cortez Hills pit dimensions: 2km long x 1km wide x 400m deep and Typical bench height 15m.

The underground mining method is underhand cut and fill with a cemented rock fill. Ore is drilled with two boom jumbos, blasted on a round by round basis, loaded into haul trucks, and hauled to surface. Parallel 5m wide by 5.5m high and 3 km declines with crosscuts at every 150m.

Three different metallurgical processes are employed for the recovery of gold; run-of-mine heap leach, conventional mill (CIL) and refractory roaster and/or autoclave. The process used for a particular ore is determined based on the grade and metallurgical character of that ore. Lower grade run-of-mine oxide ore is heap leached on existing facilities, while higher-grade non-refractory ore is treated in a conventional mill using cyanidation and a CIL process. Mill throughput varies from 10,430 to 12,698 tonnes per day (11,500 to 14,000 tons per day) depending on the hardness of the ore being processed. Refractory ore is stockpiled on site in designated areas and trucked to Goldstrike for processing.