A team of scientists have discovered trace amounts of ‘invisible’ gold can be found in iron pyrite – more commonly known as fool’s gold. The study and its findings could help offer new ways to extract this precious metal as the world’s resources slowly dwindle.
Iron pyrite has long been associated with gold due to its deceptive yellow hue. While far more common and less valuable than the real thing it does still have its uses in industry, such as lithium batteries. Pyrite can also form in an alloy with real gold, further cementing the relationship between the two.
It was known that gold could be found within pyrite, but the true scale was undetermined until the latest study by the research team at Curtin University in Perth, Australia, and the China University of Geoscience. The paper, published in the ‘Geology’ journal is titled – ‘A new kind of invisible gold in pyrite hosted in deformation–related dislocations’.
The study showed that tiny particles of gold can be found throughout the pyrite crystals. As lead research Denis Fougerouse put it, “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.”
These defects in the crystal are known as dislocations, and are a hundred thousand times smaller than the width of a human hair. At such tiny scales, atom probe tomography is required in order to detect these nanoparticles of gold.
The second part of the study was improving the efficiency of the extraction process of these tiny gold particles. With the discovery of high-grade deposits of gold declining in recent years as the finite gold resources of the Earth are mined, scientists are increasingly interested in new ways of extracting gold from other sources.
With small amounts of gold present however, extraction from pyrite needs to be cost effective, while environmental concerns remain just as important as with physical mining. On this subject Fougerouse said “Generally, gold is extracted using pressure oxidizing techniques (similar to cooking), but this process is energy hungry. We wanted to look into an eco-friendlier way of extraction. 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.”
Iron pyrite is a much more common find than high-grade gold deposits, so developing an effective way to extract even small amounts of gold could become a new avenue for the metal in the future. The techniques developed in seeing this invisible gold could also help in cataloguing gold’s distribution among other minerals.For fool’s gold however it could help further dispel the unfortunate moniker this mineral has gained over the years, and turn it into another valuable find, one that many miners of the past would no doubt be surprised to hear of.