This technical report presents the mineral processing operations, metallurgical testwork, and resource estimates for the Paroo Station lead carbonate mine as of December 31, 2014.
Report context
The Paroo Station Mine, located 30 km west of Wiluna in Western Australia, is a lead carbonate operation 100% owned by Ivernia Inc. through its subsidiary Rosslyn Hill Mining Pty Ltd. The mine was constructed during 2004, commissioned during 2005, and achieved commercial production on October 1, 2005. The mine was placed on care and maintenance in January 2015 due to low commodity prices. This NI 43-101 technical report has an effective date of December 31, 2014.
Processing route
General flow sheet
The Paroo Station Mine process plant is a conventional mineral concentrator consisting of crushing, grinding, sulphidisation, flotation and concentrate dewatering. The ore feed is an oxidised material containing lead carbonate (cerussite) as the main economic mineral. A single lead carbonate concentrate is produced for export.
Crushing and grinding
Ore is delivered to the run-of-mine pad by haul trucks from the mine. It is separated into ore stockpile fingers and withdrawn by front-end loader and blended as required. Stockpiled ore is fed into the run-of-mine bin over a static grizzly screen. Crushed ore is conveyed to a two-stage closed circuit grinding section. Primary crushed ore is fed directly to the semi-autogenous grinding (SAG) mill feed chute and ground in a SAG mill. Hydrocyclone overflow goes to the flotation feed surge tank; the underflow is divided with two thirds going to the degritting screen before returning to the SAG mill feed chute and the remaining one third going to the ball mill. The primary mill trommel can discharge directly to a scats bunker and use of the degritting screens depends on ore type.
The overflow product from both hydrocyclone clusters targets a product sizing of 80% (P80) minus 150 microns, discharging directly into a flotation feed surge tank with a live volume of 500 m³. Low grade ore scats from the SAG mill trammel and siliceous grit from the oversize of the degritting screens can be stockpiled and treated if the lead content warrants it.
Flotation and sulphidisation
Concentration of non-sulphide lead-bearing minerals is carried out by sulphidising froth flotation. Slurry from the flotation feed surge tank is pumped to the sulphidisation conditioning tank. The most important variable to control in the flotation section is the oxidation reduction potential (ORP) where the ground ore is sulphidised.
The flotation circuit consists of two parallel rougher-scavenger stages and three cleaner stages. These 6-cell banks operate on rougher and scavenger flotation duties, with the rougher/scavenger concentrate gravitating to the head of the first cleaner cells and the tailing reporting to final tailing. First cleaner tailing goes to final tailing. Final lead concentrate assays around 65 to 69% lead.
Concentrate dewatering and handling
Flotation concentrate is thickened to 67% w/w solids by two thickeners in series , a 6 m diameter thickener followed by a 9 m diameter clarifier, with the clarifier overflow gravitating to the process water dam. Underflow from both thickeners is pumped to a thickened concentrate storage tank and then filtered to 8.5% w/w moisture.
Lead concentrate with a moisture content of at least 7.5% is loaded at the mine site into specially designed two tonne United Nations and Western Australia state government-approved bulk bags. Once filled and sealed, the bags are vacuumed to remove any stray dust and placed into sealed and bolt-locked steel standard shipping containers. The sealed steel shipping containers containing bagged concentrate are transported by road from the Paroo Station Mine to Wiluna and on to Leonora, then from Leonora to the port at Fremantle by rail for shipment overseas.
Tailings handling
Final tailing is thickened to approximately 48% w/w solids in a 16 m diameter high rate thickener, with the underflow pumped in two stages to the tailings storage facility and the overflow going to the process water pond for recycling.
Process control
Process monitoring and control is done by a Citect SCADA system, with the concentrator having typical measurement equipment for a modern flotation plant such as a multi-stream on-stream analyzer unit.
Historical operating performance
Throughput of between 1.4 Mtpa and 1.7 Mtpa has been demonstrated through the concentrator. Annualised 2014 throughput exceeded 1.4 Mtpa. Historic operating data supports average recoveries above 79%; however, recovery is highly dependent on the feed grade and other variables being maintained.
Proposed design parameters
The mine plan reports that the operation has a life of just over 4 years remaining consisting of 6.8 million tonnes ore at 7.0% lead. An economic cut-off grade of 5.0% Pb was used in the analysis. The process recovery of lead is linked to lead head grade. The following recovery formula was used in the analysis: Pb Recovery = (-0.385*(Pb²)+7.889*Pb+43.15)/100. The average recovery is 78%.
Key reported parameters
| Parameter | Unit | Design Value | Historical Actual | Testwork Basis |
|---|---|---|---|---|
| Throughput | Mtpa | 1.4–1.7 | 1.44 (2014 annualised) | , |
| Head grade | % Pb | 7.0 (mine plan average) | 7.0 (2014 average) | , |
| Lead recovery | % | 78 (formula-based average) | 79.0 (2014 average) | Recovery formula: (-0.385*(Pb²)+7.889*Pb+43.15)/100 |
| Concentrate grade | % Pb | 67.0 (assumed for economic model) | 67.4 (2014 average) | , |
| Concentrate moisture | % w/w | ≥7.5 (shipping requirement) | 9.2 (2014 average) | , |
| Flotation feed sizing | P80 microns | 150 | , | , |
| Concentrate thickener feed solids | % w/w | 67 | , | , |
| Final tailing thickener underflow | % w/w | 48 | , | , |
| Concentrate filter moisture | % w/w | 8.5 | , | , |
| Flotation feed surge tank live volume | m³ | 500 | , | , |
| Plant availability | % | , | 88 (2014 average) | , |
| Plant usage | % | , | 85 (2014 average) | , |
| Payable metal | % | 95.0 (economic model assumption) | , | , |
| Mine life | years | 4.17 | , | , |
| Average production rate | Mt/yr | 1.36 | , | , |
| Maximum production rate | Mt/yr | 1.78 | , | , |
| Ore milled | Dmt | 6.78 (total mine plan) | 1,437,958 (2014 total) | , |
Project website: https://en.wikipedia.org/wiki/Rosslyn_Hill_Mining
Technical qualifications
The quality of information, conclusions, and estimates contained in this report is based on: i) information available at the time of preparation, ii) data supplied by outside sources, and iii) the assumptions, conditions, and qualifications set forth in this report. This report is intended for use by Ivernia subject to the terms and conditions of its contract with the Qualified Persons, Competent Persons and relevant securities legislation. Except for the purposes legislated under provincial securities law, any other uses of this report by any third party is at that party's sole risk.
The report provides Mineral Resource and Mineral Reserve estimates, and a classification of resources and reserves prepared in accordance with the Joint Ore Reserve Committee (JORC) 2012 Code of Practice. Mineral Resources which are not Mineral Reserves do not have demonstrated economic viability. The estimate of Mineral Resources may be materially affected by environmental, permitting, legal, marketing, or other relevant issues.
The QPs have relied upon the work of others to describe project and corporate history, environmental and regulatory permitting, social or community impact, project infrastructure, general area resources, land tenure and land title, and royalties, agreements and encumbrances. These submissions have not been independently verified by the QPs.
Source: NI 43-101 Technical Report , Paroo Station Lead Carbonate Mine, effective December 31, 2014, Sections 1.4, 1.5, 1.6, 1.8, 1.12, 2.1, 3.
