Name of the Project
Prieska zinc/copper project.

Location
The project is located 270 km south-west of Kimberley, in the Northern Cape, South Africa.

Client
Orion Minerals owns an effective 73.33% interest in the project through its subsidiary companies.

Project Description
The Prieska zinc/copper deposit has been recorded as one of the world’s top 30 volcanogenic massive sulphide deposits.

The project encompasses the historical Prieska copper mine, where mining ceased in 1989. The site was closed and rehabilitated in 1991, leaving behind a significant portion of the Copperton deposit.

Initial metallurgical testwork at the proposed project has yielded positive results, demonstrating Prieska’s potential to produce high-quality marketable zinc and copper concentrates.

The project has total mineral resources of 29.4-million tonnes for 1.13-million tonnes of zinc and 360 000 t of copper.

Orion intends to establish new mining operations to continue the extraction of the remaining deposit.

Orion MD and CEO Errol Smart has indicated that the project will likely comprise an openpit and underground operation, with the openpit to produce ore while the underground operations are dewatered and re-established.

Potential Job Creation
Not stated.

Net Present Value/Internal Rate of Return
None stated.

Value
Not stated.

Duration
Orion Minerals aims to reopen the Prieska mine in 2020.

Latest Developments
Orion Minerals has completed the follow-up, locked-cycle metallurgical testwork on the deeper mineralised domains at its Prieska zinc/copper project.

The Prieska deep sulphide zone is currently the subject of a bankable feasibility study (BFS) targeted for completion in the second quarter of 2019. Initial results from the metallurgical testwork programme were reported in June, and the programme has now been completed.

Results have confirmed the metallurgical continuity of the deep sulphide zone with the up-dip area of the mineralised zone.

Recoveries of copper and zinc into separate, high-quality concentrates have been achieved using the froth-flotation process used in historical operations. In addition, the use of modern metallurgical reagents is showing encouraging results.

Meanwhile, the latest bench-scale, locked-cycle metallurgical tests have achieved targeted total metal recoveries, ranging from between 80% and 94% for zinc, and between 80% and 86% for copper into separated concentrates.

The resultant concentrates have had metal grades ranging between 45% and 54% for zinc, and between 20% and 26% for copper in the respective products.

Gold and silver are collected in the copper concentrates at levels that would qualify them as valuable by-products. The results are consistent with expectations for bench-scale testwork, which has limited stabilisation time and still provides an opportunity for improvement in continuous operations.

Meanwhile, detailed elemental analyses of the concentrates have confirmed that several key deleterious elements are at negligible levels, with arsenic, bismuth, cadmium, cobalt, tellurium, thorium and uranium at levels well below thresholds, which may attract material penalty charges from most smelters or exclude some markets.

Production scheduling using this information, Orion has noted, will further optimise resultant marketable products.

Test results, to date, have generally equalled or exceeded the metal recoveries and concentrate grades achieved during historical mining operations. Orion has explained that, when graphically superimposed over the historical plant performance dataset, the latest locked-cycle test results compare favourably with the historical operational performance.

The zinc and copper recovery results, meanwhile, correlate well with the average historical trend line.

The latest metallurgical testing programme validates this substantial historical dataset, which Orion says can now be applied, along with more recent testwork results, to formulate base assumptions for ongoing mine feasibility studies and concentrate marketing terms.

BFS. Outcomes from metallurgical testing will enable the next phase of the BFS to progress, which includes the final design of the metallurgical plant, derivation of metallurgical performance projections and optimisation of the reagent suit to improve operating efficiency and cost control.

The mineral processing plant that is being designed employs a similar flowsheet to that used in historical mining operations, albeit with the application of modern technology while reusing as much of the remaining surface infrastructure as is serviceable.

Investigations into optimising the reagent suite for the mineral processing plant are in progress to substitute the use of sodium cyanide as a zinc depressant, with sodium metabisulfite (SMBS), besides other aims.

The removal of sodium cyanide from the reagent suite will have significant economic and safety benefits for the project, reducing the cost of production, avoiding any potential exposure to sodium cyanide and eliminating the need for a detoxification section of the plant ahead of tailings storage.

Further testwork is in progress to validate that the SMBS reagent suite performs as well as the cyanide control test observations.

Additionally, Orion is investigating the establishment of new mining operations targeting the extraction of the remaining zinc/copper mineralisation at the Prieska volcanogenic massive sulphide deposit.

Mine development studies are scheduled for completion in the first half of 2019.
 
Key Contracts and Suppliers
None stated.

On Budget and on Time?
Not stated.

Contact Details for Project Information
Orion Minerals, tel +61 3 8080 7170, fax +61 3 8080 7174 or email info@orionminerals.com.au.