The CMC is a polymetallic hydrothermal, brittle low sulphidation deposit hosted in the andesitic rocks of the Rímac Formation. The veins exhibit pinch-swell type behavior typical of hydrothermal systems found within compressional and extensional structural environments. Vein widths reach upwards of 2.0 m and with a mean width of 0.6 m. The veins are known to split into two or more branches separated by waste rock materials.

The CMC property is almost entirely underlain by the Rímac Formation andesitic volcanic rocks. The base of the sequence is composed of brecciated volcanic rocks overlain by andesitic flows, agglomerate and tuff towards the top of the Cerro Huamanjune at approximately 4,500 masl elevation.

Mineralization at CMC is that of an anastomosed system where most of the secondary and tertiary veins branch off either from the main vein or the secondary veins. This has produced the necessary conduits to be filled by mineralized hydrothermal fluids. The overall system trends towards the NE at approximately 15°, and the veins are primarily sub-vertical to steeply NW dipping. It is thought that the anastomosed vein system is part of a larger tectonic shear zone with associated secondary and tertiary tensional veins.

The three main veins on the CMC property include the Wellington, Constancia and Animas veins. These veins define three structurally dislocated blocks from which a series of secondary and tertiary tensional veins splits off. The veins are extensive and are known to extend over 4 km along strike and more than 1.5 km down dip.

Typically, the veins show Qtz-clay-pyrite argillic alteration, which extends up to 2.0 m into the footwall and hanging wall of the veins. The alteration does not contain any economic mineralization of note.

Main Veins
Constancia Vein
The vein outcrops at an elevation of 4,540 masl. Nyrstar completed drilling that confirmed a down dip extension of over 300 m below the lowest mine workings. This increased the known vertical extent of the Constancia Vein to 1,700 m. The vein has a strike extent of almost 4 km, of which 2.3 km are within the CMC property.

The vein strikes towards 200° SW and dips from 75° to 80° NW. The vein widths range from 0.10 m to 1.20 m wide with a mean width of 0.54 m. Mineralization typically consists of Qtz-AsPy-Py, followed by another band of sphalerite-galena-chalcopyrite.

Wellington Vein
Similar to the Constancia Vein, the Wellington Vein is steeply dipping to the NW. The widths are also similar, with a mean of 0.64 m. The vein commonly splits into two separate branches, which have been mapped up to 1.4 m wide with some local ore shoots of up to 3.0 m in width. The vein is typically associated with clay-silica-pyrite sericite alteration in both the hanging and footwall, as well as fault gouge.

Animas Vein
The Animas Vein extends for over 1 km and has a mapped vertical extent of approximately 300 m. The vein has a mean width of 0.65 m. It was the target of exploration during the 2015 and 2016 drilling program and returned results of 3.64 grams per tonne (g/t) Au and 417 g/t Ag over 0.41 m and 1.50 g/t Au and 107 g/t Ag over 1.20 m, with minor base metals. There has been no known production from the Animas Vein.

With all of this previous activity, CMC has established mine access portals, level development, raises and underground infrastructure that, in most cases, can be utilized for future operations. The proposed CMC restart considers utilizing existing mine infrastructure, access portals, rail transfer levels, ramps, and ancillary mine systems to produce approximately 550 tpd (198,000 tonnes per year) from underground mining. Multiple veins will be mined at the same time and sequenced to maximize value. A ramp-up period will be needed since existing access levels can be rehabilitated to allow for stope development.

Due to the geometry of the mineralized zones, highly selective mining methods must be used for all veins at CMC. Two mining methods are proposed, both as variants of the overhand cut-and-fill (CAF) mining methods. In cases where the vein width is narrower than 0.50 m, resue mining will be used. Resue mining involves selectively blasting and removing mineralized material, prior to blasting waste, to make-up the total minimum mining width of 0.90 m. This mining process is slower and more labor intensive than traditional overhand CAF, but it reduces the amount of waste rock that is shipped to the process plant.

In cases where the vein width is greater than 0.50 m, traditional overhand CAF mining will be used with waste rock as the backfill. In both cases, production stope dimensions are 50 m high by 60 m along strike. These two methods have been historically used at CMC.

The PEA contemplates the following:
- Sill development will progress along the mineralized vein to provide bottom and top access for each stope.
- Raises will be developed vertically along the vein from the bottom sill to the top sill. These raises will also serve as ventilation airways and secondary egress.
- 3 m high sill and top pillars will be left in-place and not recovered.
- 1.7 m high cuts will be mined in both directions from the raise. The mineralized vein will be blasted first then slushed to the muck pass. Waste will then be blasted to make-up the 0.90 m minimum mining width. Additional waste rock will be used to backfill the cuts and provide a working floor for the next cut.
- 90% mining recovery of mineralized material is assumed (10% losses).
- All other waste rock from development activities will be hauled out of the portals to waste rock storage sites.
- Drilling will be performed using hand-held pneumatic drills while slushers and scrapers will be used in the stope to move rock.
- Low profile trucks will haul from the chutes to the closest transfer raise. From the bottom of the transfer raise, the mineralized material will typically be hauled by a rail system on the main levels.

Average productivity rates based on historical mining and updated cycle time models is assumed at 30 tpd for resue and 40 tpd for CAF per each producing stope. In order to meet desired production levels of 550 tpd, 14 to 19 producing stopes will be active at any time. In addition, 14 to 19 other stope blocks will either be in development or preparation mode (approximately 50% producing and 50% in preparation/development). This ratio is consistent with other narrow vein mines using similar mining methods and results in approximately 34 active mining areas at any given time.

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Metal recoveries are accomplished by using standard flotation methods to generate base metal concentrates for direct sale. Also included in the circuit is differential flotation of AsPy from pyrite, with the AsPy concentrate being treated by BIOX® and subsequent cyanidation for the recovery of Au and Ag.

The concentrator is primarily a base metal polymetallic sulfide concentrator producing Pb, Cu and Zn concentrates. The concentrator was expanded to include production of an AsPy concentrate which is treated via BIOX® to recover refractory Au using CIL technology. The original CMC plant was designed and commissioned in 1999 to process 600 tpd of ore primarily from the Wellington and Constancia Veins.

Flotation Circuits
The concentrator produces a Pb concentrate, containing most of the Ag, a Zn concentrate, a Cu concentrate, and an Au rich AsPy concentrate. The Pb, Zn and Cu concentrates are trucked and/or rail hauled to a concentrate buyer, located at the Por ........