Excellent summary here:Extremely impressive that the 2 strains...

Excellent summary here:

Extremely impressive that the 2 strains of microbes work in tandem, one breaking down the rock minerals while the other recovers the precious metals, then a simple cyanide leach recovers 98/94% of the gold and Pd from the solution.

https://www.innovationnewsnetwork.com/brazilian-critical-minerals-developing-brazils-critical-mineral-deposits/43944/

Três Estados precious metals project

Tres Estados started life as a gold project with assaying difficulties, and even though native metal that resembled could be seen in the core, fire assays could not detect gold or silver. It turned out, after much SEM work, the native metal was a unique alloy containing gold, platinum, copper, lead and occasional minimal amounts of osmium and iridium, which readily explained why fire assay did not work – so what would work was there an assay method for this type of metal occurrence.

There were metallurgical tests using smelting methods utilising five-kilogramme mineral samples and copper sulphate that did return assays for precious metals. These metallurgical tests were expensive and could not be used as an assay for JORC purposes, so an assay method needed to be developed.

After many years, a nickel smelt prep followed by a fire assay was developed and accepted as an assay procedure. This procedure required ten grams of mineral to be combined with laboratory-grade nickel and several fluxes to be brought to 15400C for ten minutes, which formed a nickel button. The nickel button was then dissolved in four different acids and fire-assayed for Au, Pd, Pt, Ir, and Rh, the sum of which was the basis for the existing resource, containing 725,300 ounces of combined gold, platinum, palladium, iridium, and rhodium. While the overall grade was above one gram and quite valuable because of the rhodium and iridium, the company, believing there was more there and the assays were understating the metal content, began looking for enhancements and a production method.

Ecobiome, a microbe leaching company based in Texas, came to management’s attention as a way to enhance the recovery and work as a process solution. Testing began in late 2022 and was finalised in June of 2023, indicating that Ecobiome’s proprietary microbes could achieve both enhanced recovery and production.

The final test was conducted in May of 2023 utilising drill hole TED-20, a Três Estados metallurgical test hole. The result of a 108-hour leach test utilising two of EcoBiome’s microbes that were designed to work in tandem, with one breaking down the mineral particles and the other recovering the precious metals. The results were spectacular, with a ten-fold increase in metal recovered over the nickel smelt assay. What was then BBX’s Catalão lab received 50kg of the bioleached matter for further production and recovery test work. Ultimately, of the plus 16 grams of gold and palladium released by bioleach 98% of the gold was recovered and 94% of the palladium was recovered by cyanide leaching method apply to the bioleached material. From this work, a decision was made to utilise Ecobiome’s bioleaching process to aid in re-assaying the Tres Estados resource starting at Tabocal.

All the necessary laboratory equipment and infrastructure for conducting bioleach assaying and pilot plant testing has been acquired, assembled and commissioned in the Catalão laboratory. The equipment includes nine 35-litre reactors for conducting bioleach assays (see Fig. 4) and a larger pilot plant reactor. The finalisation of the importation of the required materials from EcoBiome in Texas is currently in progress, with the commencement of routine assaying of Três Estados drill holes scheduled for early Q1 2024.