JOHANNESBURG (miningweekly.com) - JSE-listed minerals explorer Orion Minerals on Wednesday said detailed metallurgical test work will be conducted at its Prieska zinc/copper project, using 1 583 kg of diamond drill core samples obtained from mineralised intersections in 21 holes drilled across the mineralised zones of the deposit targeted for mining.

The company noted that its +105 Level Target was now being considered for mining by openpit methods, while the deep sulphide target was being assessed for extraction by underground mining methods using the significant underground infrastructure, such as shafts and declines, remaining from the historic mine.

The complete metallurgical test work programme will comprise flotation scouting, flotation optimisation, comminution characterisation, variability assessments and advanced design work to determine the most profitable process design.

Based on metallurgical test results obtained to date, the copper-rich material from the deep sulphide target responded well to a differential rougher float, achieving 89.5% copper rougher recovery to the copper concentrate and 93.4% zinc rougher recovery to the combined copper and zinc concentrates, under optimal rougher flotation conditions.

The zinc-rich material from the deep sulphide target also responded well to a differential rougher float, achieving 88.9% copper rougher recovery to the copper concentrate and 96.9% zinc rougher recovery to the combined copper and zinc concentrates, under optimal rougher flotation conditions.

The positive results allowed the test work programme to progress to the next phase, which entails conclusion of the scouting work on the copper-rich mineralised supergene zone of the +105 Level Target.

Further bulk flotation, differential flotation, cleaner flotation and concentrate regrind tests will be undertaken to determine the expected cleaner upgrade potential and ultimately expected concentrate grades for marketing assessments.

Further comminution characterisation and variability assessments will also be conducted as part of the detailed variability test work programme, the company said.

Orion Minerals aims to complete a bankable feasibility study on the project by the fourth quarter of this year, while the application for a mining right for Prieska will be submitted this quarter.

All mine design concepts will be finalised by the time of submission, with detailed feasibility study work to follow. Work on compiling the submission has commenced, with the mandatory survey plans being compiled, as well as all other elements of the submission being compiled, the company said.