Alvo Minerals returns ‘excellent’ recoveries from preliminary metallurgical testwork at Palma Project, Brazil

Alvo Minerals (ASX:ALV) reports it has returned ‘excellent’ recoveries from preliminary metallurgical testwork from bulk samples of mineralised Volcanogenic Massive Sulphide (VMS) samples from the Palma Project in Brazil.

The company says it sent over 315km of diamond core in 202 samples from the C3 prospect in Central Brazil to Auralia Metallurgy in Perth where the samples were selected and received under the supervision of BHM Process Consultants, and the samples were received and logged, composited and the preparation of the master composite was completed.

The master composite was selected to match the overall expected grade of the C3 VMS mineralised zone and the sample was initially tested with a 2-stage rougher floatation at P80 125um, 106um and 75um and the results were analysed for future work.

Alvo says the finest of the rougher tests (P80 at 75um) was chosen for single pass Rougher and Cleaner stage floatation tests and various samples were sent to Nagrom for assaying.

The company says 2 concentrates were separated with copper and lead reporting to the first bulk sulphide concentrate containing grades of 25.2% Cu, 3.35% Pb, 1.84% Zn, 246g/t Ag, and 0.9g/t Au. The recovery of the copper to this concentrate was over 70%, however there is significant metals in the tails which may be recovered during additional testwork.

Alvo

A calculated projected recovery to this concentrate for the copper to be confirmed by locked cycle tests currently underway is 81.1% Cu at over 20% Cu grade.

The second concentrate produced was a zinc concentrate which reported a grade of 46.2% Zn, 1.93% Cu, 0.25% Pb, 0.12g/t Au and 20g/t Ag, and the recovery of the zinc to this concentrate was over 56% however there is significant metals in the tails which may be recovered during additional testwork. Alvo estimates the overall assumed recovery of the zinc in this concentrate to be 83.3% Zn at over 50% Zn grade.

Alvo Minerals Managing Director Rob Smakman said these results represent a great step forward for the Palma Project.

“Metallurgy for VMS style projects is vital and we are really pleased with the initial results”

“Metallurgy for VMS style projects is vital and we are really pleased with the initial results. There is a lot of work still to go with the testing, however with the locked cycle tests underway, we are confident the numbers can be confirmed shortly and enhanced.

We are also extremely conscious of our sustainable mining responsibilities and are considering various options for processing. It was under this framework that we also initiated a study into converting the sulphur rich tails into sulphuric acid. We understand the tails will naturally generate acid and that the potential environmental issue will need mitigation.

The desktop study completed by our consultants has confirmed that by floating the sulphur rich minerals in the tails and passing through a separate process route, we can not only generate commercial sulphuric acid (which is sought after in the region and globally), but iron ore and more importantly, energy to power a portion of the plant. Alvo will look to incorporate the potential processing options as a key part of our ESG framework.”

Alvo reports the ongoing locked cycle testwork will better estimate the final concentrate grades and recoveries as the cleaner tails a re-circulated and this will allow for the metal in the system to either report to a concentrate or final tailing, and the deportment of gold and silver to the rougher tails is ‘low’ at 12% and 27.7%, however the feed grades are also ‘low’ at 0.09ppm Au and 24.4ppm Ag.

It also notes the arsenic rejection to the rougher tail is ‘significant’ at around 67%, and the grades observed in the final concentrates are well below normal penalty specifications, however as the target metal recoveries increase in a locked cycle, the values of the arsenic and other metals may increase.

The company reports no product marketing of the concentrates has been completed to date, however based on industry standards these concentrate grades are ‘attractive’, particularly the copper and lead concentrate, and optimisation is ongoing to elevate the zinc concentrate to over 50% contained Zn.

The metallurgists from BHM view the preliminary results as ‘extremely’ positive stating “given the very high rougher recoveries, it is projected that significant improvements in terms of both overall recovery and zinc product grade can be achieved in locked cycle testing as much of the remaining metal exists in secondary product and recycle streams, not as a loss to tailings as referenced.”

Alvo requested BHM to undertake a concept review of generating sulphuric acid from the tailings using known processing as a way of increasing sustainability credentials, mitigating environmental risk and adding another potential revenue stream to the project.

BHM reported that assuming the grade of other tailings is similar to the C3 master composite generated from the testwork stating there is ‘sufficient’ sulphur and the right mineralogy to produce a mineral concentrate that should be suitable for the production of sulphuric acid for sale, and this process will generate electrical energy from the thermal reaction on site, potentially enough to run its own plant and offset some the concentrator power demand.

Auralia Metallurgy also completed a Bond Mill closed circuit grindability test of the C3 master composite sample, and the open aperture for this sample was 106um and the resultant Bond ball mill work index was 14kW hours/dry tonne, considered medium hardness and relatively soft compared to other VMS projects on the standard scale of material property.

Alvo reports it will be completing metallurgical testwork at C3 and C1, with C3 scheduled to be completed in Q4 2022 and C1 proposed to commence in Q4 2022.

The company will also continue extensional diamond drilling at C3 targeting extensions along strike and at depth, as well as diamond drilling at new targets within the C3 cluster including Mafico, Ema, Pelicano and Pombo.

Alvo is also conducted downhole electromagnetic (DHEM) surveys at C1 and C3 on diamond holes completed in phase one and two drill programs and fixed-loop electromagnetic (FLEM) surveys on regional targets across Palma as well as geochemical sampling across all prospects and Induced Polarisation (IP) surveys at C3 and C1.

Alvo Minerals is a base and precious metals exploration company focusing on finding ‘high-grade’ copper and zinc at its flagship Palma Project in Central Brazil.

The Palma Project has a JORC 2012 inferred mineral resource estimate of 4,600,000 tonnes @ 1% Cu, 3.9% Zn, 0.4%Pb and 20g/t Ag.

Images: Alvo Minerals Ltd
Written By Harry Mulholland
Hailing from the Central Coast region of NSW, Harry is a passionate journalist with a background in print, radio and ESG news. When not bashing away on his keyboard, he can be found brewing a coffee or playing with his dog.