“Don’t let fool’s gold fool you,” scientists say

Pyrite. (Image courtesy of Curtin University).

A team of researchers from Curtin University, the University of Western Australia and the China University of Geoscience 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.

“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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