The Rosemont deposit consists of copper-molybdenum-silver-gold mineralization primarily hosted in skarn, genetically, it is a style of porphyry copper deposit, although intrusive rocks are volumetrically minor within the resource area. The skarns are formed as the result of thermal and metasomatic alteration of Paleozoic carbonate and to a lesser extent Mesozoic clastic rocks. Near surface weathering has resulted in the oxidation of the sulfides in the overlying Mesozoic units however, oxidation also occurs in the underlying Paleozoic carbonates

Garnet-diopside-wollastonite skarn, which formed in impure limestone, is the most important skarn type volumetrically. Diopside-serpentine skarn which formed in dolomitic rocks is less significant. Marble was developed in the most purest carbonate rocks, while the more siliceous, silty rocks were converted to hornfels. Both marble and hornfels are relatively poor hosts to mineralization. The main skarn minerals are accompanied by quartz, potassium feldspar, amphibole, magnetite, epidote, chlorite and clay minerals. Quartz latite to quartz monzonite intrusive rocks host strong quartzsericite-pyrite alteration with minor mineralization. Where the mineralized package of Paleozoic rocks and quartz-latite intrusive outcrop on the western side of the deposit, near surface weathering and oxidation has produced disseminated and fracture-controlled copper oxide minerals. The Mesozoic and lesser Paleozoic rocks above the LAF are propylitically altered to an assemblage including epidote, chlorite, calcite, and pyrite. Copper mineralization is irregularly developed. The rocks are commonly deeply weathered and limonitic. The original chalcopyrite is typically oxidized to chrysocolla, copper wad and copper carbonates. Supergene chalcocite is locally present.

Three mineralization domains (oxide, mixed and sulfide) were defined based on the soluble to total copper ratio (ASCu/TCu) collected in the Augusta (2005 to 2012) and Hudbay (2014 and 2015) drilling programs. The oxidation and mixed mineralization occurs mainly above a low angle fault defining the contact between the Palozoic and Mesozoic rocks as chrysocolla, copper carbonates and supergene chalcocite.

Mineralization is mostly in the form of primary (hypogene) copper, molybdenum and silver bearing sulfides, found in stockwork veinlets and disseminated in the altered host rock. Some oxidized copper mineralization is also present in the upper portion of the deposit. The oxidized mineralization is primarily hosted in Mesozoic rocks, but is also found in Paleozoic rocks on the west side of the deposit and deeper along some faults. The oxidized mineralization occurs as mixed copper oxide and copper carbonate minerals. Locally, enrichment of supergene chalcocite and associated secondary mineralization are found in and beneath the oxidized mineralization.

The Rosemont deposit is a high-tonnage, skarn-hosted, porphyry-intruded, copper-molybdenum deposit located in close proximity to the surface. The Project will be a traditional open pit shovel/truck operation. It consists of open pit mining and flotation of sulfide minerals to produce commercial grade concentrates of copper and molybdenum. Payable silver and gold will report to the copper concentrate.

The proposed pit operations will be conducted from 50-foot-high benches using large-scale mine equipment, including: 10-5/8-inch-diameter rotary blast hole drills, 60 yd3 class electric mining shovels, 46 yd3 class hydraulic shovels, 25 yd3 front-end loaders, and 260-ton off-highway haul trucks.

The Rosemont final pit will measure approximately 6,000 feet east to west, 6,000 feet north to south, and will have a total depth of approximately 2,900 feet down to 3,100 feet (AMSL). There is one primary waste rock storage area (“WRSA”), which is located 1,200 feet southeast of the Rosemont final pit.

The mine phases and ultimate pit for the Project are designed for large-scale mining equipment (specifically, 60 yd3 class electric shovels and 260-ton haulage trucks) and is derived from the selected LG pit shells described in the previous section. The design process included smoothing pit walls, eliminating or rounding significant noses and notches that may affect slope stability, and providing access to working faces by developing internal ramps (including a dual ramp for the final pit). For the pit design, the targeted minimum mining width is 320 ft. and honored the wall slope design provided by Call and Nicholas, Inc. (“CNI”) and Hudbay.

Total ore reserves in the final pit are estimated to be 592 million tons. Approximately 55 million tons of medium and low grade oxide, mixed and sulfide ore will be stockpiled. This material will be reclaimed and processed during operations.

The Rosemont process plant includes the following unit processes and facilities:
- Primary crushing.
- Crushed ore stockpile and reclaim.
- Parallel SABC grinding lines with pebble crushing.
- Copper flotation comprising rougher flotation, concentrate regrind, and two stage cleaning.
- Cu-Mo concentrate thickening.
- Molybdenum flotation including roughing, concentrate regrind and five stages of cleaning.
- Molybdenum concentrate thickening, filtration and drying.
- Copper concentrate thickening and filtration.
- Copper concentrate load out and storage.
- Tailings thickening, filtration and dry stacking.
- Reagents storage and distribution (including lime slaking, flotation reagents, water treatment and flocculant).
- Grinding media storage and addition.
- Water services (including fresh water, fire water, gland water, cooling water and process water).
- Potable water treatment and distribution.
- Air services ( ........