Column: Electric dreams turn into a nightmare for battery metals
A sector that was once racing to build new supply has been closing mines and deferring projects as low prices bite into the cost curve.
A team of researchers from Curtin University, the University of Western Australia, and the China University of Geoscience have discovered that tiny amounts of gold can be trapped inside pyrite, making ‘fool’s gold’ more valuable than its name suggests.
In a paper published in the journal Geology, the scientists present an in-depth analysis to better understand the mineralogical location of the trapped gold in pyrite. This review — they believe — may lead to more environmentally friendly gold extraction methods.
According to the group, this new type of ‘invisible’ gold has not been previously recognized and is only observable using a scientific instrument called an atom probe.
The gold is hosted in nanoscale defects called dislocations – one hundred thousand times smaller than the width of a human hair
“Previously gold extractors have been able to find gold in pyrite either as nanoparticles or as a pyrite-gold alloy, but what we have discovered is that gold can also be hosted in nanoscale crystal defects, representing a new kind of ‘invisible’ gold,” lead researcher Denis Fougerouse said in a media statement.
According to Fougerouse, the more deformed the crystal is, the more gold there is locked up in defects.
The scientist explained that the gold is hosted in nanoscale defects called dislocations – one hundred thousand times smaller than the width of a human hair – and this is why it can only be observed using atom probe tomography.
Following their discovery, Fougerouse and his colleagues decided to look for a process that allowed them to extract the precious metal using less energy than traditional pressure oxidizing techniques.
Selective leaching, which involves using a fluid to selectively dissolve the gold from the pyrite, seemed like the best choice.
“Not only do the dislocations trap the gold, but they also behave as fluid pathways that enable the gold to be ‘leached’ without affecting the entire pyrite,” the researcher said.
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Everaldo Gonçalves
O ouronano ou ouro invisível já está bem conhecido em escala experimental de bancada no Brasil. O geólogo brasileiro Ysao Munemassa e sua equipe há mais de duas décadas estão pesquisado esse ouro não detectado em análise químicas tradicionais, em jazidas primárias hidrotermais, principalmente, encaixadas em formações com rochas com quartzo e biotita e nos descartes dessas minas, com sucesso na recuperação de nanoouro não detectado na análise química no fire assay e na leitura final na absorção atômica. Por informação verbal de ensaios em ensaios de bancada amostras de minério com 1 grama de ouro por tonelada que os garimpeiros e mineradores conseguem recuperar na concentração gravimétrica foram recuperados teores de 10, 13 e até analise de 23 gramas de ouro por tonelada. O método surpreendente é revolucionário e está na fase final de teste em laboratório com minério de várias regiões para poder entrar na etapa de testes nas lavras. Saudações aos autores Denis Forgerouse e seus colaboradores e ao colega Ysao Munemassa, Everaldo Gonçalves, geólogo.