Cerro de Pasco Resources Advances Metallurgical Test Program; Evaluates Two-Concentrate Flowsheet for Silver-Bearing Pyrite and Base Metals

MONTRÉAL, June 09, 2026 (GLOBE NEWSWIRE) — Cerro de Pasco Resources Inc. (TSXV: CDPR / OTCQX: CDPMF / BVL: CDPR (Lima) / FRA: N8HP) (“CDPR” or the “Company”) is pleased to provide an update on the status of the integrated metallurgical test program advancing the Quiulacocha Tailings Reprocessing Project in central Peru. The results obtained to date, across multiple laboratories and over 110 individual tests, support a directional path toward a two-concentrate flowsheet, each concentrate carrying silver, and show strong metallurgical responsiveness of the Phase 1 Quiulacocha tailings samples to conventional and emerging flotation technologies.

Highlights:

• Conceptual flowsheet with Two Concentrate Streams: Metallurgical testing in bench-scale and mini-pilot programs has converged on a conceptual flowsheet generating a high-grade pyrite concentrate and a base metal concentrate, both containing silver (see Figure 1 below).
• Pyrite concentrate stream under evaluation: With pyrite representing more than 50% of the Quiulacocha tailings portion drilled in 2024, the Company is investigating a pyrite concentrate stream as an alternative source of sulphur for essential industries such as phosphate-based fertilizers and chemical reagents used in critical-metal processing.
• Strong silver and sulphide recovery at bench-scale and mini-pilot testing: In the mini-pilot plant to date, greater than 92.5% of total sulphides and approximately 94% of silver (lattice-bound and discrete) were recovered into a bulk concentrate, together with the associated base-metal sulphides.
• Low sulphide tailings: Importantly, the final tails are targeted to contain low residual sulphur, which test results indicate may reduce acid-generation potential a key objective of the Company’s remediation strategy, subject to further test work.
• Further optimization work underway: Bench and pilot-scale programs will continue to refine the flowsheet to produce indicative concentrate specifications to form the basis for subsequent technical studies and for initial discussions with potential strategic offtake and investment partners.
• Gallium and Indium: Mineralogical studies highlight opportunities to concentrate gallium and indium. This is leading to targeted exploratory metallurgical test-work focused on the silicate fraction of the tails to investigate gallium recovery, and on the base metals and pyrite concentrate to determine indium recovery. This test-work is at early, exploratory stage and any potential is conceptual.

Steven Zadka, Executive Chairman, commented: “This program has moved us from promising bench-scale results to a continuous mini-pilot test an important step in evaluating a project of this scale. The results to date show strong recovery of silver and sulphides into a single bulk sulphide concentrate, as first step in the conceptual flowsheet. Critically, a high portion of the silver is recovered with the sulphides rather than lost to tails, and our program is designed to investigate silver recovery through downstream processing of the pyrite concentrate not only to rely on its payability in a pyrite product. The pyrite dominance of these tailings is the reason we are pursuing a two-concentrate flowsheet: the pyrite stream has potential value as a sulphur-bearing feedstock in a market where conventional supply is tightening. Significant work remains separation into a cleaner pyrite concentrate, roasting and calcine studies, and offtake discussions but this material must ultimately be addressed, and we intend to be the ones to address it.”

Conceptual Metallurgical Flowsheet

The conceptual flowsheet under development is built around a sequential flotation route designed to optimize total sulphide recovery while producing two concentrates under evaluation. A simplified schematic is shown below.

Figure 1: Overview of Tailings Reprocessing Flowsheet Concept

The re-mined tailings, following any required classification and/or regrinding, are first directed to a bulk sulphide rougher flotation stage operating at acidic pH (typically 4.55.5). This approach leverages the natural floatability of pyrite under acidic conditions, without lime suppression, and concurrently recovers the associated base metal sulphides and silver-bearing minerals into a high-grade bulk sulphide concentrate. Non-sulphide gangue (predominantly quartz and manganese-rich siderite) reports to the final tails, which can be returned to a controlled tailings storage facility.

The bulk sulphide concentrate is then directed to a base metal flotation stage where the contained sphalerite, galena, copper sulphides and some of the silver-bearing minerals are separated from the pyrite. This produces:

• A base metal concentrate (potentially as one or two streams), carrying zinc, lead, copper, silver.
• A pyrite concentrate at grading 9095% pyrite, targeting a combined low zinc-plus-lead content, potentially suitable for sulphuric-acid production (via roasting), precious-metal recovery, and emerging sulphur-supply applications.

The flowsheet is conceptual and remains under active optimization. This program is being evaluated using conventional mechanical cells, as well as specialized fine-grain flotation cells, in order to identify the optimal combination of recovery, grade and capital efficiency.

Quiulacocha Mineralogy Overview

An in-depth mineralogical characterization program, incorporating quantitative TIMA (TESCAN Integrated Mineralogical Analysis) and Zeiss-Mineralogic automated mineralogy, electron microprobe, sequential extraction, hydroseparation and laser-ablation ICP-MS, has been completed on multiple tailings samples collected during the 2024 drilling program (Phase 1), as well as on concentrate products. The mineralogy is materially driving flowsheet selection.

Key Mineralogical Observations

Pyrite-dominant feed: The portion of the Quiulacocha tailings drilled in 2024 is mineralogically dominated by pyrite, which represents in excess of 50% of the bulk material (Figure 2). This is notably high relative to typical polymetallic tailings and is the principal driver of the two-concentrate-stream approach. Pyrite liberation is generally good (typically 6589%, and over 90% in pyrite concentrate samples; Table 1).

Figure 2: Modal mineralogical composition from two composites from the Quiulacocha Tailings generated from Phase 1 drill cores. Mineral Liberation Analysis performed by Erzlabor, in Freiberg (Germany), through measurement mode GXMAP (Grain X-ray Mapping) in July 2025

Table 1: Liberation analysis for pyrite in feed, bulk sulphide concentrate and tails. Mini-Pilot Plant Test MG#6 (completed 13 March 2026). SGS Mineralogy Report, Phase 1, SGS-Santiago.

Mineral / Mass [wt%]	Feed MG#6	Conc Final MG#6	Tailings Final MG#6
Free (95% area)	78.73	80.86	56.28
Lib (80% area & 50% perimeter)	11.09	10.95	13.87
Mid (50% area & 20% perimeter)	5.73	5.35	12.16
Sub Mid (20% area & 10% perimeter)	3.13	2.47	6.65
Locked	1.32	0.37	11.04
Total	100.00	100.00	100.00

Silver association with sulphides: Silver occurs as lattice-bound silver within sulphides (based on microprobe analysis, Universidad de Barcelona, Spain) and as discrete minerals (argentite/acanthite (AgS) and matildite (AgBiS)), intimately associated with pyrite, mainly as inclusions (Zeiss-Mineralogic, Luleå University of Technology, Sweden). Consequently, a high proportion of silver reports to the bulk sulphide concentrate and would subsequently distribute to pyrite and base-metal concentrate streams.

Together, these mineralogical findings explain why the bulk-sulphide-first flowsheet under investigation delivers more consistent results: it captures the silver and base metals that are mineralogically locked with pyrite, before applying selective separation chemistry to a lower-mass concentrate stream.

Table 2: Modal composition for feed, bulk sulphide concentrate and tails associated with Mini-Pilot Plant Test MG#6. SGS Mineralogy report, Phase 1

Sulphides and gangue minerals	Feed MG#6	Con MG#6	Tails MG#6
Copper sulphides	0.02	0.05	0.00
Sphalerite	1.95	1.83	0.94
Galena	0.35	0.43	0.23
Pyrite	54.24	89.74	3.81
Pyrrhotite	0.40	0.26	0.01
Arsenopyrite	0.19	0.25	0.04
Quartz	15.61	2.50	37.29
Other silicates	0.08	0.27	1.72
Fe Oxides/Hydroxides	0.34	0.02	0.52
Carbonates (Mostly siderite)	25.05	3.23	53.97
Sulphates & Phosphates	1.02	1.38	1.44
Others	0.01	0.02	0.01
Total	100.00	100.00	100.00

Gallium and Indium: Geochemical (Sequential leaching) and mineralogical studies (TIMA; LA-ICPMS, SEM) show gallium is deporting to the crystalline lattice of gangue minerals like kaolinite and Aluminium-Phosphate-Sulphate (APS) mineral phases. These minerals, preferentially reporting to tailings after bulk sulphide concentration, represent an opportunity for reverse or selective concentration to increase overall gallium content. In addition, indium is primarily associated with sphalerite, the main zinc-bearing mineral, and therefore reports to the base metals stream. Exploratory work for gallium and indium concentration is being studied through bench-scale tests and currently waiting for first results. Metallurgical parameters defined after best bench-scale result will eventually be used in dedicated mini pilot plant runs.

Laboratory Bench-scale Tests

The mini-pilot plant campaign at SGS Santiago builds on, and corroborates at continuous scale, a structured bench-scale test program comprising more than 110 individual flotation tests conducted across multiple internationally recognized laboratories including Maelgwyn (United Kingdom), Plenge (Peru), XPS (Canada) and SGS (Chile). The program was organised into two complementary workstreams: 65 sequential flotation tests evaluating the staged recovery of copper-lead, zinc and pyrite into separate concentrates; and 45 pyrite-focused flotation tests assessed under three distinct scenarios (selective precious-metal recovery, bulk sulphide concentrate, and sulphur-optimized pyrite concentrate).

The 12 selected bench-scale rougher tests, together with MG#6 mini-pilot result in Table 3 and Figure 3 indicate that, on the samples tested, a single bulk-sulphide flotation stage recovers a large proportion of silver (8795%) and pyrite (9399%) into a concentrate, together with a significant proportion of the zinc (6282%) and lead (6078%). These recoveries reflect a bulk-sulphide pull of approximately 67% of feed mass, consistent with the sulphide-dominant nature of the tailings; the bulk concentrate is an intermediate step, subsequently separated into pyrite and base-metal concentrates.

The first mini-pilot campaign at SGS Santiago (test MG#6) returned recoveries that fall within the bench-scale range on every metal reported – silver, zinc, lead and sulphur – providing an initial indication of scaled-up reproducibility.

The results presented in the table and chart are exploratory in nature, relate only to the specific samples and conditions tested, and have not been demonstrated at commercial scale. Further test work, completion of the Phase 2 drilling and resource-definition programs, metallurgical testing on Phase 2 samples, and additional engineering studies are required before any conclusions can be drawn about the deposit as a whole or about the characteristics of any contemplated product stream.

Table 3: Summary of bench scale and mini-pilot results relevant to the bulk-sulphide flotation (prior to base metal flotation). These results do not represent the final targeted pyrite concentrate

Test				Head grade
Test ID	Composite	Lab	Type	Ag (g/t)	Au (g/t)	Cu (%)	Pb (%)	Zn (%)	As (%)	Fe (%)	S (%)
FT-5	25-0009-GM	Plenge	Bench	55.62	0.14	0.14	1.14	1.43	0.30	34.69	33.96
F007	25-0009-GM	XPS	Bench	52.65	n.r.	0.12	0.88	1.48	0.25	31.45	29.51
KF-5	25-0005-GM	Plenge	Bench	47.83	n.r.	0.09	0.95	1.54	n.r.	30.93	27.97
FT-1	25-0009-GM	Plenge	Bench	45.77	0.15	0.11	0.87	1.51	0.25	29.67	29.85
FT-39	26-0001-BK	Plenge	Bench	45.42	0.04	0.03	0.49	1.17	0.19	32.11	30.29
FT-41	26-0001-BK	Plenge	Bench	45.45	0.04	0.03	0.47	1.25	0.19	32.64	29.66
FT-37	26-0001-BK	Plenge	Bench	46.39	0.04	0.03	0.50	1.22	0.19	31.91	29.89
FT-2	25-0009-GM	Plenge	Bench	45.76	0.14	0.11	0.82	1.49	0.23	29.39	29.71
FT-7	25-0009-GM	Plenge	Bench	45.93	0.13	0.12	0.87	1.53	0.24	29.57	29.47
FT-40	26-0001-BK	Plenge	Bench	45.22	0.04	0.03	0.51	1.19	0.18	32.26	28.85
FT-42	26-0001-BK	Plenge	Bench	44.65	0.04	0.04	0.50	1.20	0.19	32.16	29.29
FT-4	25-0009-GM	Plenge	Bench	37.40	0.17	0.09	0.37	1.65	0.17	26.94	27.64
MG#6	26-0001-BK	SGS Chile	Mini-pilot	49.20	n.r.	0.03	0.52	1.13	n.r.	34.10	28.70

<td style="border-right: solid black 1pt ; border-bottom: solid black 1pt ; text-align: center ; ve

Test

Mass

Recovery (%)

Conc. grade

Test ID

Composite