Global Gold Mining Hits 91% Gold Recovery at Sturec Ahead of Feasibility Study
Key Takeaways
- Metallurgical testwork at ALS Metallurgy in Perth returned gold recoveries of 91.4% from Fresh composites and 91.0% from Channel composites at the Sturec Gold deposit in Slovakia.
- Mining One Consultants confirmed that 91% gold recovery is achievable using a relatively simple flotation flowsheet — no gravity circuit required — which supports a lower-cost plant design.
- The Transitional composite returned a lower recovery of 79.5%, attributed to partial oxidation of that material zone, an expected characteristic rather than a process failure.
- Results will directly inform the processing component of the Sturec Pre-feasibility Study, converting metallurgical assumptions into defensible economic inputs for plant design and cost estimates.
- Further metallurgical testwork is planned using drillcore from the current drilling programme, with the scope of that work guided by these initial results.
Sturec metallurgical results deliver 91% gold recovery ahead of PFS
Global Gold Mining (ASX: GGM) has released results from a metallurgical testwork programme on composite samples from the Sturec Gold deposit in Slovakia, with gold recoveries to flotation concentrate reaching 91.4% from Fresh composites and 91.0% from Channel composites. The testwork was completed at ALS Metallurgy in Perth under the supervision of Mining One Consultants.
These results will directly inform the processing component of the Sturec Pre-feasibility Study (PFS) and guide the scope of further metallurgical evaluation planned using drillcore from the current drilling programme.
Mining One Consultants
“The results of the Sturec metallurgical testwork programme are highly encouraging. In particular, gold recoveries of 91% from Fresh variability testing can be achieved using a relatively simple flotation flowsheet. The testwork has also demonstrated that gravity-recoverable gold can effectively be recovered through flotation, potentially simplifying the overall process flowsheet. The results provide increased confidence in the metallurgical characteristics of the Sturec mineralisation and represent a positive step in de-risking the Project as it progresses toward future development studies.”
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How the testwork programme was structured
The programme followed a sequential optimisation methodology, beginning with a Master composite (head grade 1.26 g/t Au) before advancing to variability testing on three distinct composites. This staged approach means each phase of testing informed the conditions used in the next, rather than running isolated experiments in parallel.
From master composite to variability testing
The optimisation sequence on the Master composite proceeded as follows:
- Grind optimisation: Initial rougher tests returned gold recovery of 93.4% at a grind size of P80 53 µm and 88.9% at P80 75 µm. (P80 refers to the particle size at which 80% of the material passes through a screen.) Subsequent work used the coarser P80 75 µm grind. Note these are rougher-stage results, distinct from overall recovery to final concentrate.
- Gravity Recoverable Gold (GRG) assessment: GRG tests returned an average gravity gold recovery of approximately 23%. Comparative tests showed that gravity-plus-flotation and flotation-only approaches returned similar gold recoveries under the conditions tested, so subsequent testwork omitted the gravity circuit.
- Rougher-concentrate regrind testing: Regrind tests evaluated reducing the particle size of the rougher concentrate before cleaner flotation. A regrind size of P80 15 µm was selected for subsequent work.
- Cleaner flotation stage evaluation: Two- and three-stage cleaner tests showed limited upgrade in the third cleaner stage. Subsequent testwork therefore used two stages of cleaning.
The selected final conditions were: P80 75 µm primary grind, rougher-concentrate regrind to P80 15 µm, two cleaner stages, and no gravity circuit.
Variability test results at a glance
Three variability tests were then run using these selected conditions on Fresh, Transitional, and Channel composites. The Transitional composite returned a lower recovery of 79.5%, which the announcement attributes to partial oxidation of that material. This is an expected characteristic of transitional-zone material rather than an indicator of process failure.
| Composite | Au Head Grade (g/t) | Au Recovery to Concentrate (%) | Concentrate Au Grade (g/t) |
|---|---|---|---|
| Fresh | 0.97 | 91.4 | 20.2 |
| Transitional | 1.29 | 79.5 | Not disclosed |
| Channel | 2.89 | 91.0 | 84.4 |
The arithmetic average of the Fresh and Channel gold recoveries is 91.2%. The announcement notes this figure excludes the Transitional result and is not a deposit-wide or production-weighted recovery. The results relate to the tested composites and laboratory conditions; flotation recovery to concentrate does not represent final downstream metal recovery or payable metal.
What flotation metallurgy means for gold project development
Metallurgical testwork establishes how effectively gold can be extracted from mined rock using a given processing method. For investors evaluating a gold development project, recovery rates are one of the most material economic inputs available before a feasibility study is complete. Here is what the key concepts mean in plain terms:
- Flotation flowsheet: A processing method that separates gold-bearing minerals from waste rock by conditioning crushed material with water and chemical reagents, then introducing air bubbles. Gold-bearing particles attach to the bubbles and float to the surface, where they are collected as a concentrate.
- Why a “simple” flowsheet matters: Fewer processing stages generally mean lower capital expenditure to build the plant and lower operating costs per tonne processed. Mining One’s comment that a “relatively simple flotation flowsheet” can achieve 91% recovery is therefore commercially meaningful, not just technical.
- What a PFS uses these results for: A Pre-feasibility Study (PFS) translates geological and metallurgical data into an economic model. Recovery rates feed directly into production assumptions, plant design specifications, and processing cost estimates. Without testwork data, those inputs are estimates; with it, they become defensible figures.
- Why 91% is a strong result: For epithermal-style gold deposits (low-temperature, near-surface gold systems like Sturec), recoveries in the high-80s to low-90s are generally considered strong. Achieving 91% with a straightforward two-stage flotation circuit, and without a gravity circuit, supports a simpler and potentially lower-cost plant design.
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Next steps toward the Sturec PFS
The results will now feed directly into the processing component of the Sturec PFS. Further metallurgical testwork is planned using drillcore from the current drilling programme to support future studies, with the current results expected to inform the scope of that work, including variability assessment across the material proposed for processing.
Key points for investors tracking GGM’s development timeline:
- Metallurgical results from this programme inform PFS processing assumptions, plant design, and cost estimates.
- Further testwork is planned using core from the ongoing drilling programme, with current results guiding the scope of that additional work.
- Testwork was conducted at ALS Metallurgy in Perth and supervised by Mining One Consultants, both widely recognised parties in Australian gold project evaluation.
- The Competent Person for this announcement is Mr Louis Cohalan, a Member of the Australian Institute of Geoscientists and a full-time employee of Mining One Consultants Pty Ltd.
De-risking the metallurgical component of a PFS is a defined step in a structured path toward a development decision. The processing flowsheet at Sturec is becoming better defined, and the results support a straightforward flotation circuit. For investors following GGM’s progress, that is a meaningful reduction in one of the key uncertainties that typically precedes a PFS.
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