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.

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

The mine was operated from 1971 to 1991, after which it was closed and the site rehabilitated.

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 results confirm that the remaining Prieska mineralisation, intersected to date, also responds well to metal concentration using froth flotation and recoveries, which might match or exceed historical performance.

Optimised rougher flotation conditions to produce differentiated copper and zinc concentrates from the deep sulphide target have also been determined, as have preliminary rougher conditions to produce a bulk copper and zinc concentrate from the shallow 105 Level target (openpit). Historical rougher flotation conditions have been improved through varying reagent dosages and supplementary modern reagents. 

The resultant rougher products are well suited to upgrading in cleaner circuits to produce saleable products. Cleaner flotation testwork is continuing. 

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.

The baseline project that Orion is evaluating envisages the mine producing about 100 000 t/m. 

This rate would translate into 12 000 t/y to 15 000 t/y of copper concentrate and 20 000 t/y to 25 000 t/y of zinc concentrate – consistent with the mine’s historical output.

Potential Job Creation
Not stated.

Net Present Value/Internal Rate of Return
None stated.

Value
Not stated.

Duration
The project could start production by 2020. The project timeline envisages the completion of a Joint Ore Reserves Committee- (Jorc-) compliant resource estimate by the first quarter of 2018, the lodging of a mining right application in the second quarter, feasibility study results by the fourth quarter and the start of construction of the plant in mid-2019. 

The proposed underground operation will likely start production by 2022.

Latest Developments
Orion Minerals has successfully completed the development of a mineral flowsheet for the treatment of sulphide zinc/copper mineralisation at the Prieska project.

The derived mineral processing flowsheet achieves high zinc and copper recoveries into separated product streams from which the production of high-quality, differentiated zinc and copper concentrates can be yielded.

The processing flowsheet has been tested with notable success on all the mineralised zones of the Prieska deposit that are targeted in the bankable feasibility study (BFS) that is under way.

The deposit is zoned for metallurgical testing by the degree of oxidation (shallow supergene and deep hypogene zones), while the internal variation in zinc and copper grades relative to each other across the deposit has also considered zinc- and copper-dominant zones.

Representative core samples for the testwork were collected from holes drilled by Orion across these different grade and oxidation zones, as noted in a release in November last year.

Most significantly, effective zinc and copper separation has now been achieved from samples collected within the supergene horizon of the deposit, while maintaining acceptable metal yields from the copper and zinc circuits for differentiated concentrates.

This, the company has noted, is a significant improvement on the metallurgical performance achieved by historical mining operations and from earlier testwork.

Results of the successful completion of Phase 1 were reported in November 2017, confirming that the targeted mineralisation at the Prieska deposit was amenable to processing using froth flotation. 

The results achieved from Phase 2 testwork are indicative of how the derived flowsheet performs with respect to recovering and separating targeted metals, the company has said. 

However, ongoing optimisation aims to improve the resultant concentrate qualities to equal or better the metallurgical performance that have been reported to have been achieved during historical mining operations.

Over the 20-year mine life, metal recoveries averaged 85% for zinc and copper into concentrates that had concentrate grades ranging from 28% to 30% for copper (in the copper concentrates) and from 51% to 53% for zinc (in the zinc concentrates).

The company has further indicated that the metallurgical testwork results achieved to date confirm that the Prieska deposit is amenable to efficient treatment applying widely used and well understood mineral-processing techniques, as well as standard, widely available reagents.

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.