This Preliminary Economic Assessment for the Olza zinc-lead project in southwestern Poland is based on Inferred Mineral Resources and proposes an underground mining operation with conventional flotation processing.
Report context
The Olza Project Preliminary Economic Assessment (PEA) Technical Report, dated May 2015, was prepared in accordance with National Instrument 43-101 standards. The project is located in the Upper Silesian Mineral District in southwestern Poland, approximately 60 km northwest of Krakow. The property comprises three exploration concessions Zawiercie, Rokitno, and Chechlo with a total surface area of 152.65 km². Rathdowney Polska holds the concessions through its parent company Rathdowney Resources Ltd. (RTH). The PEA is preliminary in nature and includes Inferred Mineral Resources that are considered too speculative geologically to have the economic considerations applied that would enable them to be categorized as Mineral Reserves. There is no certainty that the PEA will be realized.
Processing route
Metallurgical testwork program
The metallurgical and mineral processing aspects of the PEA were completed by Melis, based in Saskatoon, Saskatchewan, Canada. The first phase of metallurgical testwork was completed at SGS Minerals Services UK Ltd near Truro, Cornwall, UK, under the direction of Melis. A single composite was prepared and tested, made up from core selected by geologists from RTH from 25 drillholes representing the Olza mineralization styles in proportion to their relative abundance in the documented resource area. The average test head grade of the overall test composite was 6.1% Zn and 1.4% Pb for a combined head grade of 7.5% Zn+Pb.
Comminution testing
A sample of the test composite was submitted for a Ball Mill Bond Work Index test, resulting in a Ball Mill BWI measurement of 10.6 kWh/t, indicating that the Olza mineralization is relatively soft.
Flotation testwork
The preliminary test program showed that the Olza mineralization responded well to standard lead and zinc flotation conditions without any upgrading ahead of flotation. Primary grind rougher flotation tests showed that a primary grind K80 of 90 µm (80% passing size) would maximize metallurgical efficiencies. Lock cycle testing of the test composite yielded a projected zinc recovery of 92% to a zinc concentrate containing 58% Zn, with low projected iron content at less than 0.5% Fe. Projected lead recoveries were 90% to a lead concentrate containing 70% Pb.
Proposed process flowsheet
Based on preliminary metallurgical testwork, the proposed process flowsheet consists of Semi-Autogenous Grinding and ball milling followed by standard flotation treatment. Mill feed will be ground to 80% passing 90 µm size and subjected first to lead flotation at natural pH with one cleaning stage to produce a lead concentrate grading 70% Pb. The lead flotation tails would be subjected to zinc flotation at elevated pH with one cleaning stage to produce a zinc concentrate grading 56% Zn. Based on the quality of zinc concentrate produced in the lock cycle test, which was low in iron (less than 0.5% Fe) and magnesium (less than 2% Mg), acid leaching of the zinc concentrate has not been included in the process. Tailings slurry will be discharged to a lined Tailings Management Facility with reclaim water recycled for re-use in the mill process.
Target recoveries and concentrate grades
The results of the lock cycle test were adjusted to show the PEA run-of-mine grade for the Olza deposit. Target recoveries and grades for the anticipated mill feed grade of 4.98% Zn and 1.50% Pb are 89% zinc recovery to a zinc concentrate assaying 56% Zn and a lead recovery of 88.5% to a lead concentrate grading 70% Pb. With a mill throughput of 2.16 Mtpa, estimated concentrate production rates are 171,000 tpa of zinc concentrate and 41,000 tpa of lead concentrate. Pressure filtration of the concentrates will reduce the moisture content to less than 10% prior to shipment to smelters.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Throughput | 6,000 | tpd | Design target |
| Annual throughput | 2.16 | Mtpa | Design target |
| Ball Mill Bond Work Index | 10.6 | kWh/t | Testwork result |
| Primary grind size (K80) | 90 | µm | Testwork recommendation |
| Head grade (PEA life-of-mine) | 4.98 Zn, 1.50 Pb | % | From mine schedule |
| Zinc concentrate grade | 56 | % Zn | Target from testwork |
| Zinc recovery | 89 | % | Target adjusted from testwork |
| Lead concentrate grade | 70 | % Pb | Target from testwork |
| Lead recovery | 88.5 | % | Target adjusted from testwork |
| Zinc concentrate iron content | Less than 0.5 | % Fe | Testwork result |
| Total installed power process plant | 10,710 | kW | Design estimate |
| Total installed power underground mine | 2,350 | kW | Design estimate |
Project website: https://www.openair-museum.pl/en/dzialy/Olza-mityczna-i-historyczna-EN/The-Olza-in-painting-and-photography
Technical qualifications
The PEA is based on Mineral Resources, not Mineral Reserves. Mineral Resources do not have demonstrated economic viability. The PEA is preliminary in nature and includes Inferred Mineral Resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as Mineral Reserves. There is no certainty that the PEA will be realized. The metallurgical testwork was conducted on a single composite sample from 25 drillholes, and the projected recoveries and grades have been adjusted from lock cycle test results to show life-of-mine grades. There are no Mineral Reserves defined for the project.
Source: Olza Project Preliminary Economic Assessment, May 2015. Relevant sections: 1.11 Metallurgical Summary, 1.15 Recovery Methods, 1.15.1 Recoveries and Concentrates.
