Why Juniors Are Re-Drilling Copper Porphyries Majors Abandoned

A copper porphyry abandoned by a major looks like a verdict on the rock. At Copper Cliff in Montana, that verdict rested on holes that stopped at 300-400 m. Years later, deeper holes drilled by Kennecott/Rio Tinto reported 1,252 m of mineralisation starting at 665 m, which is below where the original drilling ended. Copper porphyry exploration often turns on questions like this: did the first owner test the system, or only its upper section?

The question has a live price attached. LME three-month copper traded at about US$14,628/t on 13 October 2026, according to Reuters, and juniors are picking up projects that majors set aside.

Mogotes Metals (TSXV: MOG) is running two of these second tests. Copper Cliff tests depth, and Beskauga in Kazakhstan tests drilling cost. Two projects do not establish an industry-wide trend.

This piece sets out how to judge whether a second test is rational, which results would support or undermine it, and a practical checklist you can apply to any junior buying a dropped asset.

Why do majors drop copper porphyries, and what does “dropped” actually mean?

The instinctive reading is simple: a major had the money, the geologists and the data, and it walked away, so the project must be poor. That reading assumes the decision was about the rock. Often it was not.

A porphyry is a large, low-grade copper system formed around an intrusion of cooled magma. Its economics depend on scale, because each tonne carries little metal. A typical economic range is about 0.2-0.5% copper equivalent, and the outcome depends on throughput, recovery, strip ratio, infrastructure and capital intensity. For these deposits, the owner’s other options matter as much as the geology.

Because porphyry copper deposits derive their value from sheer scale rather than grade, a hole that stops in the upper section of the system can understate what sits beneath, which is why drilling depth matters so much to the second-test question.

Published commentary points to four reasons majors exit:

1. Capital allocation. Wood Mackenzie’s 2025 analysis described a shift toward capital discipline and production growth.
2. Scale and grade thresholds. The project is too small or too low-grade for a major’s portfolio.
3. Depth and follow-up cost. Deeper holes give better information but take a disproportionate share of capital.
4. Jurisdiction and permitting. Mining.com reported that Chilean permitting for large porphyries can take roughly 12 years, and that discovery to production can take more than 17 years.

Mogotes CEO Allen Sabet gives a concrete case. In 1992, he said, Newmont’s global team had richer, easier options, including direct-shipping ore in Papua New Guinea and the DRC. Against those, deep drilling in Montana did not compete.

Key distinction “Dropped” does not necessarily mean “geologically invalid.” It may mean the project failed one owner’s hurdle at one point in the commodity cycle.

A major’s exit therefore says little about the geology and a lot about that major’s priorities. Your first question should be which of the four reasons applied. Some exits do hide real problems, and that selection risk comes up again below.

Copper Cliff: can deeper drilling turn old intercepts into a deposit?

Copper Cliff shows the depth question most clearly. Newmont drilled the property in the 1990s and found no significant mineralisation, but its holes ended at 300-400 m.

Kennecott/Rio Tinto later drilled deeper and hit long mineralised intervals. Mogotes has not verified these historical results.

Peter Ellsworth, then a Newmont geologist, argued in his master’s thesis that the 1990s holes tested only the top of a deeper porphyry. He is now Mogotes’ project manager and Qualified Person (the accountable technical expert) for Copper Cliff. The site has seen no exploration since 2017.

The USGS porphyry copper deposit model describes systems with vertical extents of several kilometres, which is why holes ending at 300-400 m can test only the upper section of a deeper system.

The planned programme includes:

• 8,000-9,000 m of drilling, subject to permits
• A budget of about US$5.5 million this year
• Mother-daughter drilling, in which a parent hole runs to about 1 km and daughter holes branch from it off a single pad
• An earliest start of November 2026, with permits still pending at the 22 September 2026 update

The best intervals begin at 665 m and 785 m. At those depths, a 0.34% copper grade needs either a higher-grade core or a large-scale mining method to be economic. Copper Cliff is a bet on finding better grade at depth, not on confirming what has already been drilled, and outstanding permits put it earlier in the cycle than Beskauga.

Beskauga: does cheap drilling change the economics of a second look?

The figure that changes the Beskauga decision is cost. Mogotes cites about US$100/m for diamond drilling, which produces solid rock core, and about US$60/m for reverse circulation (RC) drilling, which produces rock chips faster and more cheaply. Sabet says drilling that is close to an order of magnitude cheaper changes how decisions get made.

East Star Resources reports Kazakhstan diamond costs of US$100-110/m, falling to about US$85/m on campaigns above 20,000 m. No independently verified per-metre figure for comparable North American or Chilean drilling was found. Per-metre figures also differ in what they include, such as drill type, depth, logistics, assay preparation and season, so they are not like-for-like.

Mogotes holds a three-year option to acquire 100% of Dostyk LLP, the licence holder, for US$24.7 million, with payments weighted toward the end. A previous junior held the option for about five years before it lapsed. Mogotes has started a programme of up to 50,000 m, costing about C$8 million.

The historical NI 43-101 estimate (a Canadian disclosure standard), effective 20 February 2022, has not been verified as current by Mogotes’ Qualified Person. “Indicated” carries more geological confidence than “Inferred”.

What has to happen before the historical numbers count

1. Verify the historical database independently.
2. Integrate the 18,657 m of drilling completed after the estimate.
3. Update the geological interpretation.
4. Produce a new estimate at current metal prices.

Roughly 40 m of clay overburden covers the project, so surface methods are ineffective and drilling is the main exploration tool. The site has a 1,100 kV power line, water from the Irtysh River and year-round access. Mogotes targets first assays in Q4 2026 and a preliminary economic assessment (PEA) within 12 months, and it has submitted a mining-licence application.

Turning a historical figure into a current mineral resource estimate means validating the database, integrating new drilling, and re-running the geological model, which is why a pre-2022 number cannot simply be carried forward.

Cheaper metres let Mogotes run more tests per dollar. That cost edge answers the tonnage question faster; it is not evidence that the resource will grow. When you assess a cost claim, ask what the figure includes and whether the comparison is like-for-like.

How much risk do earn-ins and jurisdiction really remove?

Each mechanism in these deals reduces a specific risk. Low-cost drilling buys more metres for each dollar. Mother-daughter drilling reuses pads and access. Historical data narrows the search, and staged earn-ins spread acquisition capital over time.

At Copper Cliff, Mogotes commits C$4 million in year one and C$16 million over three years to earn 51%. A further C$40 million by year six would take its interest to 60%. Rio Tinto holds a clawback, or buy-back right: if it exercises it, Mogotes spends US$32 million to take back 2%, leaving Mogotes with 49%.

Sabet calls a 49% outcome acceptable. A clawback would be a meaningful signal, because it would show a major judging that the system meets its own scale and grade criteria.

The earn-in does not remove risk. It converts geological risk into funding and dilution risk.

Several reasons for scepticism remain:

• Historical estimates are not automatically current resources.
• A major may have left for reasons that public drill results do not show, such as metallurgy, water or social licence.
• Deep low-grade economics are highly sensitive to capital costs and mining method.

Kazakhstan’s fiscal regime is changing, so project-specific tax advice matters. These deals do not eliminate risk. They move it into funding, dilution, fiscal terms and permitting, and you can weigh those against your own tolerance.

A checklist for judging juniors that buy dropped assets, and the results that would test the thesis

The analysis above reduces to a set of tests you can apply this week:

1. Why the major left: Is the full technical, permitting and commercial explanation available?
2. Data quality: Have collars, surveys, assays and QA/QC been validated?
3. Geology and mining method: Does the model identify a higher-grade core, and does depth imply block caving (a large-scale underground method)?
4. Metallurgy: Has testwork been done before the company drills heavily?
5. Economics: Does the project hold up under a lower copper price and higher capital costs?
6. Deal terms and title: What are the cash needs, dilution, back-in rights and royalties, and what failure criteria has the company set in advance?

Precedents worth calibrating against

BHP’s completion release values the Filo acquisition at about C$4.0 billion. That price reflects a mature discovery, not an early-stage system. NGEx’s valuation is also reported inconsistently: C$5.07 billion on 13 October 2026 and C$4.87 billion on 14 October 2026.

Skeena’s Khyber Pass shows historical core earning a second test. Passiflora/Titan MT‘s 843.9 m at 0.214% CuEq and Linderos at 0.23% CuEq below 1 km show how hard long low-grade intercepts are to interpret. No database of re-drilled porphyries that went on to fail was found, so these examples skew toward successes.

Large-scale copper systems in British Columbia show how long low-grade intercepts are being reinterpreted as North American mining economics shift toward scale, a useful comparison for Copper Cliff’s deep intervals.

Decide in advance which announcements would change your view. Setting failure criteria first is the main protection against holding on after a thesis breaks.

What a second look can and cannot prove

The second-test thesis holds up under disciplined conditions. The case is clearest at Beskauga, while Copper Cliff is still waiting on permits.

Cheap drilling and staged earn-ins improve capital efficiency. They do nothing to settle scale, depth, metallurgy, permitting, financing or the economics of building a mine.

The next markers are the Q4 2026 Beskauga assays and the Copper Cliff permit decision. Write down your failure criteria before either arrives.

This article is for informational purposes only and should not be considered financial advice. Investors should conduct their own research and consult with financial professionals before making investment decisions. Past performance does not guarantee future results, and forward-looking statements are speculative and subject to change.