Bioleaching test work of a composite sample from BBX Minerals’ (ASX: BBX) Três Estados gold project in Brazil has delivered an increased recovery of 5E precious metals (gold, platinum, palladium, iridium and rhodium).

The 5 kilogram sample came from one drillhole at the Adelar prospect where a maiden mineral resource was announced in October of 590,300 ounces of combined 5E metals.

The sample was taken from a homogenised 50.4kg composite comprised of hematite-altered mafic intrusive from 28 metres to 64m, believed to be typical of the altered gabbro within the Adelar resource envelope.

This interval reported 1.34 grams per tonne 5E platinum group metals (0.04g/t gold, 0.04g/t palladium, 0.71g/t platinum, 0.54g/t iridium and 0.01g/t rhodium) using BBX ́s proprietary in-house assay method.

Untreated samples were initially assayed for gold, platinum, palladium, iridium, and rhodium by an independent analytical test laboratory in Arizona and the dried samples then re-assayed subsequent to bioleaching.

Microbial technology

Bioleaching was conducted by EcoBiome Metals LLC in Texas and aimed to demonstrate how the Três Estados complex mineralisation responds to the agency’s Cultured Gold and Gold DRIVE microbial technology.

The patent-pending formulae was used to prove the ability to extract and recover 5E precious metals from an unprocessed ore sample.

Test results showed a recovered grade of 95.38g/t 5E precious metals (14.13g/t gold, 79.27g/t palladium, 0.17g/t platinum, 0.72g/t iridium and 1.1g/t rhodium).

BBX said the results were intended for test work purposes only and may not be indicative of the overall resource mineralisation.

Additional work would be required on composites from above and below the sample zone as well as on a representative composite sample from all holes incorporated in the Adelar resource estimate.

Impressed by results

BBX chief executive officer Andre J Douchane was impressed by the test results.

“These results are excellent especially since the material used was from the Três Estados JORC resource area,” he said.

“The results also include numbers describing the reduction of certain minerals during the process, which are important in helping understand where the precious metals are attached within the resource.”

Promising method

BBX technical manager Edmar Medeiros said EcoBiome’s recovery process presents itself as a “promising method” for recovering noble metals.

“The results show a significant concentration of noble metals in the ore after microbial action and confirm a significant reduction in the levels of silicon, aluminum, iron, calcium and magnesium during the process,” he said.

“The reduction in the content of these chemical elements, which make up the main minerals present, may be related to the release of precious metals and provide for their recovery.”

He said the remainder of the 50kg sample would be used for pilot plant testing scheduled to start before year end.

Ema assays

BBX has completed 5E precious metals assaying on samples from a 2017 drilling program at the nearby Ema gold project.

One of the holes returned 1m at 1.72g/t gold from 64m but no other significant results were obtained.

Holes focused on significant historical artisanal gold workings in the felsic volcanics.

At that time of drilling, the company was not aware of the presence of complex gold-PGM mineralisation hosted in the gabbro bodies.

Drill holes from the 2021 program will be assayed in the new year and will include holes drilled at the Baiano and Ema Central targets, which intersected gabbro.

BBX last week received initial results from EcoBiome’s bioleaching tests on a 1kg surface bulk sample of mafic intrusive from the Ema project.