Invisible gold seen for the first time

Gold in pyrite

A Curtin University research team in Western Australia has uncovered the nature of invisible gold trapped in pyrite and developed an eco-friendlier way to extract it.

The phenomenon of gold trapped in pyrite has been commonly known as ‘fool’s gold’ but  remained unrecognised at this depth until the research took place.

Lead researcher Denis Fougerouse said the research was increasingly important as global gold was consumed and new methods were called upon.

“The discovery rate of new gold deposits is in decline worldwide with the quality of ore degrading, parallel to the value of precious metal increasing,” Fougerouse said.

“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.

Fougerouse detailed the research methods in more depth.

“The more deformed the crystal is, the more gold there is locked up in defects. The gold is hosted in nanoscale defects called dislocations – one hundred thousand times smaller than the width of a human hair – so a special technique called atom probe tomography is needed to observe it.”

A significant goal of the research was to conserve energy, as previous methods involved with ‘fool’s gold’ extraction had proven costly.

“Generally, gold is extracted using pressure techniques (similar to cooking), but this process is energy hungry. We wanted to look into an eco-friendlier way of extraction,” Fougerouse said.

“We looked into an extraction process called selective leaching, using a fluid to selectively dissolve the gold from the pyrite. 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 paper was titled ‘A new kind of invisible gold in pyrite hosted in deformation–related dislocations’ and was published in the journal Geology by researchers from Curtin University, the University of Western Australia and the China University of Geoscience.

 

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