Image: Gold nugget found in the field.
Original Published Date: 
Friday, April 28, 2017

Dr Frank Reith—an ARC Future Fellow in The University of Adelaide’s School of Biological Sciences and Visiting Fellow at CSIRO Land and Water at Waite—is part of a team of researchers that have been investigating the role of microorganisms in gold transformation.

In the Earth’s surface, special ‘nugget-producing’ bacteria can be dissolve, disperse and reconcentrate gold into nuggets. This is called the biogeochemical cycle of gold. Dr Reith’s research team has discovered that this bacteria may hold the key to more efficient processing of gold ore, mine tailings and recycled electronics, as well as aid in exploration for new deposits.

“In the natural environment, primary gold makes its way into soils, sediments and waterways through biogeochemical weathering and eventually ends up in the ocean. On the way bacteria can dissolve and re-concentrate gold – this process removes most of the silver and forms gold nuggets,” said Dr Reith.

“We’ve known that this process takes place, but for the first time we’ve been able to show that this transformation takes place in just years to decades—that’s a blink of an eye in terms of geological time.”

Published in the journal Chemical Geology, the research team has showed that five ‘episodes’ of gold biogeochemical cycling had occurred on each gold grain studied. Each episode was estimated to take between 3.5 and 11.7 years—a total of under 18 to almost 60 years to form the secondary gold.

“These results have surprised us, and lead the way for many interesting applications such as optimising the processes for gold extraction from ore and re-processing old tailings or recycled electronics, which isn’t currently economically viable,” said Dr Reith.

Media issued by The University of Adelaide.

Photo credit: 

Image credit: The University of Adelaide/ Joel Brugger.