Copper Flat Project, US

In June 2020, New Mexico Copper and New Mexico Mining and Minerals Division (MMD) signed an agreement for the actions required to develop the mine under the New Mexico Mining Act Rules.

An updated feasibility study of the project was prepared and published with an effective date of 11 December 2018 and an issuing date of 9 April 2020.

According to the updated feasibility study, the project is expected to process 10.8 million tons per year on an average for 113.1 million short tons (total) over the expected mine life of 11.1 years.

Copper Flat Location and Site Details

The Copper Flat Project is located in the Hillsboro Mining District of South-Central New Mexico, Sierre County.

The mine lies approximately 150 miles south of Albuquerque, New Mexico and approximately 20 miles south-west of Truth or Consequences, New Mexico.

Truth can be accessed by a paved highway of 24 miles in length and by a three-mile all-weather road made of gravel.

Copper Flat is located within the USGS Hillsboro NM quadrangle north of New Mexico State Highway 152 between Caballo and Hillsboro communities.

Copper Flat Project Ownership History

The Placer and lode Gold was first produced in 1877 from the Hillsboro Mining District, New Mexico. The placer and lode gold were produced over the next 100 years valued at $8.5m.

Mostly, gold and silver were produced from underground and placer operations located in and around the project.

Gold was recovered initially by arrastras (stone grinding) followed by stamp mills before 1881. In 1881, Gold Dust, a tent city, was founded for mining placer gold deposits.

In 1892, a copper-matte smelter of 30tpd capacity was built in the Hillsboro Town. The smelter operated until early 1900’s. The Stenburg Copper Mine operated and located at the project between 1911 and 1931. Until 1941, small-scale copper and precious metals mining was conducted in the district.

The district was explored by Newmont Mining Company in 1952 for copper and then by Hilltop Mining, Bear Creek Mining Company, and Inspiration Development Company.

Hilltop Mining was working for the project between 1958 and 1959. Inspiration acquired Copper Flat in 1967 and leased it to Quintana Minerals in 1974.

Quintana formed a partnership with Phibro Minerals Enterprises, resulting in the Copper Flat Partnership in 1979 and financed by Canadian Imperial Bank of Commerce (CIBC) located in Toronto, Ontario, Canada.

Inspiration leased its mining claims in August 1987 to Hydro Resources with a purchase option finalised by 1989. The project was optioned by Rio Gold in 1989 from Hydro.

In 1989, the Copper Flat Partnership included Copper Flat Mining Co. Ltd, a Rio Gold subsidiary, controlled the project and held the property till 1993 when the project was optioned by Gold Express. Gold Express acquired the project from Rio Gold to enable the project’s operation employing 1982 design parameters.

In June 1994, Alta Gold acquired the project from Gold Express. Alta held the project till its bankruptcy in 1999.

Hydro received the property back in 2001 with the project and GCM (the vendors). NMCC acquired an exclusive option over the property from the vendors in July 2009 and made the final payment on the exclusion option in May 2011 thereby, owning 100% of the property.

Copper Flat Geology and Mineralisation

The Animas Hills and the Hillsboro District have a dominant geological feature, a Copper Flat stratovolcano. The stratovolcano is a circular body of Cretaceous andesite with a diameter of 4 miles.

The historical drill holes show that the andesite is locally more than 3,000 feet thick indicating that the local geology represents a deeply eroded Cretaceous-age volcanic complex when combined with the concentric fault pattern.

The core of the complex is a Cretaceous- age Copper Flat Quartz Monzonite (CFQM) (75 million years before present) stock intruding the middle of the andesite sequence.

The site hosts three structural zones: the Hunter Fault Zone or the Hunter and Parallel Faults, the Patten and Greer Faults or the Patten Fault Zone, and the Olympia and Lewellyn Faults. Of these, the most prominent one is the Hunter Fault Zone.

The emplacement of CFQM is largely controlled by three structural zones: the southern contact parallels cut by the Greer fault, the southeastern contact, and the southwestern contact located parallel to the Olympia and Lewellyn faults.

The CFQM contains pyrite and chalcopyrite dominantly with subsidiary molybdenite, and minor bornite, gold, and silver.

The sulphide mineralisation is hosted within the quartz monzonite as veinlets and disseminations. The sulphide mineralisation is followed by breccia pipe and coarse clotty pyrite, chalcopyrite, veinlet- controlled molybdenite, milky quartz, and potassic alteration.

The breccia pipe includes rotated angular to subangular fragments of quartz monzonite from 1 inch to more than 18 inches in diameter. Two types of breccias have been identified, biotite breccia and feldspar breccia, as different units.

The molybdenum occurs as quartz veins or as thin coatings on fractures. In the CFQM stock, carbonate and quartz veinlets host minor sphalerite and galena.

Mineral Resources and Reserves

The measured mineral resource estimate for the Copper Flat Project at a grading of $6.11 Net Smelter Return (NSR) per ton is 126,655Ktons containing 709,268lbs copper at a grading of 0.28%, 22,798lbs molybdenum at a grading of 0.009%, 380ozs gold at a grading of 0.003Oz/ton, and 7,599ozs silver at a grading of 0.06Oz/ton.

The indicated mineral resource estimate at $6.11 NSR/Ton grading is 178,571Ktons containing 678,570lbs copper at a grading of 0.19%, 17,857lbs molybdenum at a grading of 0.005%, 357ozs gold at a grading of 0.002Oz/ton, and 7,143ozs silver at a grading of 0.04Oz/ton.

The inferred mineral resources at $6.11 NST/Ton grading are 27,646Ktons containing 110,584lbs copper at a grading of 0.20%, 2,212lbs molybdenum at a grading of 0.004%, 28ozs gold at a grading of 0.001Oz/ton, and 553ozs silver at a grading of 0.02Oz/ton.

The proven mineral reserves at $6.11 to $12.75 NSR cut-off grade are 78,857Ktons containing 504,685lbs copper at a grading of 0.32%, 15,771lbs molybdenum at a grading of 0.010%, 237ozs gold at a grading of 0.003Oz/ton, and 5,520ozs silver at a grading of 0.07Oz/ton.

The probable mineral reserves at $6.11 to $12.75 NSR cut-off grade are 34,227Ktons containing 171,135lbs copper at a grading of 0.25%, 4,792lbs molybdenum at a grading of 0.007%, 103ozs gold at a grading of 0.003Oz/ton, and 1,369ozs silver at a grading of 0.04Oz/ton.

Mining Methods and Processing of Ore

The Copper Flat Project will be mined using conventional hard rock open pit mining methods. The production is planned at 29,600 tons per day (tpd) for the first six years followed by 27,125tpd for the remaining mine life.

Currently, the bench heights are planned to be 25 feet high, and drilling will be completed with three rotary blast hole rigs of 45,000lb pull-down capacity.

The rocks after blasting will be loaded into 100-ton haul trucks using two front-end loaders of 19 cubic yards.

The ore is medium hard and can undergo copper/molybdenum flotation producing copper and molybdenum concentrates.

The process for recovering copper and molybdenum minerals starts with crushing and grinding of the run-of-mine ore by a gyratory crusher. The crusher reduces the ore size to less than 175mm and conveys the coarse ore to a covered stockpile.

The coarse ore reclaimed from beneath the stockpile is conveyed to a semi-autogenous mill (SAG) of 32*14 feet for primary grinding and then to a 24*35-foot ball mill.

The ball mill works in a closed circuit with hydro cyclones to supply slurry with 80% of the particles less than 140 microns (µ) to the flotation circuit.

A part of the slurry underflow from hydro cyclones enters a Knelson-type gravity concentrator circuit to collect gravity-recoverable gold.

From the concentrator circuit, the bulk copper-molybdenum concentrate enters the flotation circuit where the concentrate is separated by a series of six 9,000 cubic foot rougher flotation cells resulting in a final copper concentrate and a molybdenum concentrate.

The final copper concentrate consists of a combination of tailings from the copper-molybdenum separation flotation and molybdenum first cleaner flotation cells.

The copper concentrate is transferred to the copper concentrate thickener, then to a copper concentrate stock tank, and finally to an automatic pressure filter for copper concentrate. The concentrate is loaded into highway haul trucks and transported to the market.

The molybdenum concentrate flows by gravity from the third molybdenum cleaner column cell to the molybdenum filter feed tank feeding the molybdenum filtering and drying circuit.

The filter cake is conveyed to the molybdenum concentrate storage bins and transported to the market in 2-ton super sacks.

Infrastructure

The existing infrastructure (estimated value of $53.9m) of the project includes concrete foundations, structures needed for the primary crusher, a concentrator, a mine substation, a truck shop, and assay lab, and an administrative building.

The other existing facilities include conveyor tunnels, a coarse ore stockpile reclaim system, four freshwater wells, eight miles long 20-inch steel pipeline to transfer water from the well field to the site, several mine roads including over 2 miles of mine haul roads and service roads, and a 2.5-mile gravel access road connecting the site to the State Highway 152.

A water diversion structure and channel, a mill site, a mine shop grading, storm water culverts, and nearly 2 million tons of pre-preproduction stripping to expose the ore body.

For the power supply, there exists a 12-mile long 115kV power line and structures connecting the mine substation to the utility power grid.

The new infrastructure will be built which includes a tailing storage facility, road improvements, railcar loading facilities, and a new substation.

Significant upgrades to the facilities include a freshwater supply system upgraded with groundwater pumps, pumping stations, and water line improvements, stockpiles, 115kV power line , and water supply.

Power Supply and Transmission

A new substation and a switch will be built at the 345kV power line at or close to the point crossing the existing 115kV line to the mine. The new substation will convert power to 115kV to supply it to the mine.

The new substation will bring 345kV power from an El Paso Electric Transmission Main Line and supply it to the Quintana 115kV line.

The existing 115kV line (high power transmission line) terminates approximately 1,000 feet from the substation of the mine and will be extended to the substation.

From the mine substation, a new 24.9kV line will be constructed connecting the substation to the freshwater well field located 8 miles to the east. The 24.9kV power line will supply power to the wells.

A diesel-powered generator of 1,800kVA and 4.16kV power will be used to supply power for the thickener pumps, rakes, area ventilation, heat tracing, limited lighting in the concentrator, mine shop, and warehouse building during power outages.

Contractors Involved

The updated feasibility study of April 2020 and the positive feasibility study of 2013 of the project were prepared by M3 Engineering & Technology Corporation.

The BLM selected Mangi Environmental Group to draft the EIS of the project in June 2012.