The Brucejack Deposit is interpreted to be a deformed porphyry-related transitional to intermediate sulphidation epithermal high-grade gold-silver vein, vein stockwork, and vein breccia deposit that formed between 184 to 183 Ma (Board and McNaughton 2013; Tombe et al. 2018; Board et al. submitted). High-grade gold-silver mineralization was formed in association with a telescoped, multi-pulsed magmatic-hydrothermal system beneath an active local volcanic center (Board et al. submitted).

Visible gold and silver mineralization in the Brucejack Deposit occurs as electrum and is predominately hosted in quartz-carbonate to carbonate vein and vein breccia structural corridors within broader stockwork zones (McPherson 1994; Kirkham and Margolis 1995; Tombe et al. 2018; Board et al. submitted). Additionally, lowgrade (less than 5 g/t) gold mineralization occurs sub-microscopically in vein- and wall rock-hosted arsenian pyrite (invisible gold) throughout the Valley of the Kings Zone and possibly within the West Zone as well. Electrum-bearing quartz-carbonate veins and stockwork overprint and are co-spatial with earlier porphyry-related phyllic alteration in the Brucejack Deposit.

The Valley of the Kings Zone is currently defined over 1,200 m in east-west extent, 700 m in north-south extent, and 650 m in depth. Deep drilling has indicated that the alteration, mineralization, and veining in this zone extend to a depth of at least 1,100 m. Mineralization in the Valley of the Kings Zone is open to the east, west, and at depth. Deep exploration drilling conducted under the Flow Dome Zone in 2018 was successful in confirming the presence of Valley of the Kings Zone-style mineralization from the eastern edge of the Valley of the Kings Zone to beneath the Flow Dome Zone, which lies approximately 1,000 m further east. The West Zone is currently defined over 590 m along its northwest strike, 560 m across strike, and down to 650 m in depth, is open to the northwest, southeast, and at depth to the northeast. The Valley of the Kings Zone contains higher gold and lower silver grades than the West Zone.

Precious metal mineralization is ubiquitous throughout the vein systems, however, its continuity is not correlated to any specific geologic continuity; although mineralized structural corridors can be continuous on the meters- to tens-of-meters scale, the within-vein gold and silver distribution is highly erratic. Nevertheless, the distribution and grade of precious metal mineralization within the mineralized structural corridors within the broader stockwork system is of significant economic interest.

The updated underground mine design supports the extraction of 3,800 t/d of ore through a combination of transverse and longitudinal LHOS. Closely matching the previously stated plan disclosed in the 2014 FS (Ireland et al. 2014), paste backfill and trackless mobile equipment will be employed in the majority of mining activities.

Access to the mine is via the Valley of the Kings decline, situated near the concentrator. The Valley of the Kings decline is also utilized as a conveyor way, with two conveyors installed at a combined length of 800 m. The existing West Zone portal provides the main access for large underground equipment and waste haulage.

Development initiated during the two pre-production years of the LOM continues, with the mine operating at a rate of 2,700 t/d since commercial production began in July 2017. The ramp-up period to a maximum output of 3,800 t/d occurs over three years, with production over this time averaging 1.3 Mt annually.

The Brucejack Property mineralization typically consists of quartz-carbonate-adularia, gold-silver bearing veins, stockwork and breccia zones, along with broad zones of disseminated mineralization. There is a significant portion of gold and silver present in the form of nugget or metallic gold and silver.

The concentrator was designed to process gold and silver ore at a nominal rate of 2,700 t/d to produce gold doré and gold flotation concentrate. The mill was successfully commissioned between March and May of 2017 and reached full operation in Q4 2017. In 2018, various review and assessment work was conducted to evaluate the potential of increasing mill throughput to 3,800 t/d and potential bottlenecks that may limit a further increase in the mill feed rate. Equipment suppliers and independent consultants conducted various reviews through various supporting test work and simulations. The review work indicated that with some minor modifications, such as increasing some of the slurry pump sizing and increasing the second and third cleaner flotation capacities, the process plant can handle the increased throughput of 3,800 t/d. The upgraded flowsheet remains identical to the existing operation flowsheet, including the following components:

- one stage of crushing underground
- a 2,500 t semi-autogenous grinding (SAG) mill feed surge bin on surface
- a SAG mill/ball mill/pebble crushing (SABC) primary grinding circuit equipped with a gravity concentration circuit
- rougher flotation and scavenger flotation of hydrocyclone overflow
- three stages of cleaner flotation on combined rougher and scavenger concentrates
- flotation concentrate dewatering
- flotation tailings dewatering circuits.

The mill feed ore is crushed and ground to the particle size of 80% passing approximately 90 to 100 µm. Two gravity centrifugal concentrators, together with two upgrading tables and one associated gravity centrifugal concentrator, recover the free nugget gold grains from the ball mill discharge. The resulting gravity concentrate is further refined in the gold room on site to produce gold-silver doré.