Mr. Stephen Dunn reports

US COPPER ANNOUNCES POSITIVE LOCKED CYCLE TEST RESULTS FROM METALLURGICAL TESTWORK AT THE MOONLIGHT-SUPERIOR COPPER PROJECT

Recent metallurgical testwork conducted at ALS Metallurgy, Kamloops, Canada, under the supervision of David Middledith of Libertas Metallurgy Ltd. confirms excellent flotation response from the Superior sulphide zone at U.S. Copper Corp.'s Moonlight-Superior mining property, located in Plumas county, California.

• A resource average master composite grading 0.32 per cent Cu (copper), 2.8 g/t (grams per tonne) Ag (silver) and 0.02 g/t (gram per tonne) Au (gold) was selected from 69 intervals over seven metallurgical drill holes at Superior, providing spatial and grade representivity of the Superior sulphide zone.
• A locked cycle test using optimized flotation conditions derived from flowsheet development testwork returned a copper concentrate grading 24 per cent Cu, 1.2 g/t Au and 178 g/t Ag at a 91-per-cent copper recovery, 74-per-cent gold recovery and 78-per-cent silver recovery.
• Open circuit cleaner flotation testing on eight variability tests with copper head grades ranging from 0.14 per cent to 0.99 per cent Cu achieved average copper recovery of 84 per cent at concentrate grades of 24 per cent Cu, 0.94 g/t Au and 196 g/t Ag.
• The optimized metallurgical flowsheet employed in these tests is conventional and simple, deploying a relatively coarse primary grind P80 of approximately 200 micrometres, a moderate rougher concentrate regrind P80 of 30 to 40 micrometres, three stages of copper cleaning and typical reagent additions for copper sulphide flotation.
• Bond Ball Work Indices on five comminution composites ranged from 14.1 to 16.6 kWhr (kilowatt-hour)/tonne and SMC A x b parameters ranged from 25.0 to 28.0.

Locked cycle test flowsheet and results

A five-cycle locked cycle test was conducted on the resource average composite using the optimized flowsheet and reagent conditions shown in figure 1 in the original version of this release. The conditions for this test were determined prior to locked cycle testing via an optimization testwork program comprising of several open circuit cleaner and rougher flotation tests at ALS under project No. KM7834. A primary grind P80 of approximately 200 micrometres was deployed followed by 12 minutes of rougher flotation, with the rougher concentrate being reground to a P80 of 30 to 40 micrometres followed by three stages of copper cleaning to produce a final copper concentrate, A cleaner 1 scavenger stage was included, with the cleaner scavenger concentrate returning to the regrind mill feed. The cleaner scavenger tailings were combined with the rougher tailing to produce a final tailings product. This flowsheet arrangement is considered conventional and consistent with other copper sulphide flotation projects.

Reagents additions the company is also considered to be conventional for this type of deposit. Owing to the low pyrite content of the sample, grinding and flotation were conducted at natural pH of approximately 8.5. Forty-two g/t of PAX (potassium amyl xanthate) and 50 g/t of A3477 were added as copper and precious metal collectors and MIBC frother was dosed as required to maintain a stable froth. The mass balance results for the balance cycles (IV and V) of the locked cycle test are presented in Table 1.

The mass pull to copper concentrate was 1.2 per cent and the concentrate graded 24 per cent Cu at 91-per-cent copper recovery. Minor element scans of the final concentrate indicate that precious metals grades would expected to be payable at 1.2 g/t Au and 178 g/t Ag. Arsenic content measured 0.27 per cent As, mercury was less than one part per million Hg and MgO content was low at 0.40 per cent. The main final concentrate diluent was SiO2, measuring 13 per cent. The main opportunity for improving concentrate grades therefore points toward silica rejection, which would warrant the further investigation of gangue depressants/dispersants in the copper cleaner circuit.

Gold and silver recovery to copper concentrate were estimated to be 74 per cent and 78 per cent, respectively, based on concentrate versus feed metal units. Full metal balances for gold and silver were not conducted owing to the low precious metal head grades in the sample tested.

The stability of the locked cycle test was excellent, with minimal mass and metal variances from cycle to cycle, further highlighting the robustness of the selected flowsheet and the locked cycle test execution.

Variability cleaner test results

A total of eight metallurgical variability samples (VAR1 to VAR8) were selected from various metallurgical drill holes and depths and covering a range of copper head grades in order to provide an insight into metallurgical variability response. Copper head grades ranged from 0.14 per cent to 0.99 per cent Cu, less than 0.01 g/t to 0.04 g/t Au and 1.0 to 8.6 g/t Ag.

Total sulphur content was less than 1.0 per cent for all composites, confirming earlier modal mineralogical analysis that suggested Superior material is generally low in pyrite. Arsenic content was also low, averaging 0.007 per cent and is believed to be linked to the presence of minor enargite (Cu3AsS4). Copper deportment was dominated by chalcopyrite (CuFeS2) averaging 83 per cent, while bornite (Cu5FeS4) and chalcocite (Cu2S) comprised the balance of the copper deportment.

Each sample was subjected to a single open circuit cleaner test using the optimized conditions and flowsheet used during KM7834 LCT-23 on the resource average master composite. While the conditions were optimized for the resource average composite locked cycle test, optimization for each variability composite was not conducted therefore the results from these tests ought to be considered indicative. The results of the open circuit cleaner tests for each variability composite are summarized below.

Copper recovery to copper concentrate ranged from 71 per cent to 90 per cent, averaging 84 per cent, while copper concentrate grades ranged from 18 per cent to 28 per cent, averaging 24 per cent Cu. All tests posted copper concentrate grades greater than 20 per cent Cu with the exception of VAR3 (medium grade shallow) and the main concentrate diluent for this sample was SiO2 comprising 26 per cent of the final concentrate mass. The presence of flotable silicate gangue in this sample may also have been the driver for the low recovery of 71 per cent. Further optimization of gangue depressants would be expected to improve this result and possibly improve the concentrate grades for all composites where silicate gangue was diluting the final concentrates.

It should be noted that the variability composite flotation results were not obtained from locked cycle testing and incremental gains in copper recovery to final concentrate would be expected for all variability samples once tested in closed circuit.

While not fully optimized, the variability test data set generally confirms the excellent metallurgical performance observed in locked cycle testing of the resource average composite, but further optimization of reagent dosages would be required to maximize individual test recoveries and concentrate grades.

Stephen Dunn, chief executive officer of U.S. Copper, commented: "The key objectives of these studies were to both confirm the metallurgical recoveries used in our preliminary economic assessment and to provide the additional new detail to begin a prefeasibility study (PFS) in the future. We are very pleased that these objectives have been met and over the next 12 months, we will finalize the PFS metallurgical testing and associated trade-off studies to support this PFS which is fundamental to our future permitting activities, aiming to eventual production."

About U.S. Copper Corp.

U.S. Copper controls approximately 10 square miles of patented and unpatented federal mining claims in the Light's Creek Copper district in Plumas county, northeast California; essentially, the entire district. The district contains substantial copper sulphide and copper oxide resources in three company-owned deposits -- Moonlight, Superior and Engels, as well as several partially tested and untested exploration targets.

The Superior and Engels mines operated from about 1915 to 1930 producing over 161 million pounds of copper with silver and gold credits from over four million tons of rock containing 2.2 per cent copper.

The Moonlight deposit was discovered by Placer Amex during the 1960s and a resource was calculated after the drilling of over 400 holes. A development decision was made but then put on hold in 1972 when copper prices were weak.

U.S. Copper has owned the Moonlight-Superior project since 2013 and has advanced it with three different drill programs and a number of engineering studies.

U.S. Copper recently reported an after-tax NPV (net present value) of $1,075-million (U.S.) in a preliminary economic assessment (PEA) prepared by Global Resource Engineering Ltd. (GRE) dated Dec. 16, 2024, with a life of mine production of 1.8 billion pounds of copper (see news release dated Jan. 6, 2025).

GRE calculated a new mineral resource for the purposes of this PEA that included all recent drill programs on the property. This resource is summarized in the attached table.

Qualified person

The scientific and technical content of this press release has been reviewed and approved by David J. Middleditch, BEng, MIMMM, independent metallurgical consultant with Libertas Metallurgy Ltd. who is a qualified person as defined in National Instrument 43-101 -- Standards of Disclosure for Mineral Projects. Mr. Middleditch is a professional member of The Institute of Materials, Minerals and Mining (UK), registration No. 676614.

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