“There’s gold in them thar hills”, says Colonel Mulberry Sellers in Mark Twain’s 1892 novel, The American Claimant. There might have been some truth in it then but, these days, gold prospectors could do better by sampling termite mounds and leaves from acacia trees. New research in Western Australia reveals where remaining gold deposits might be hiding.

Across the world, most of the easy gold (outcropping at the Earth’s surface) has already been found and gold miners have to be a bit more cunning. One area that hasn’t been searched thoroughly is underneath sediments and soils. But how does a modern gold prospector know where to start digging?

Ravi Anand, from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), and his colleagues gathered hundreds of samples of sediments, soil and acacia leaves from Moolart Well gold deposit, 400km north-east of Kalgoorlie. After analysing the gold content of all the samples they showed that clusters of gold occurred in zones rich in organic carbon (carbon derived from living material). Their findings are published in Geology.

Anand and his colleagues believe that much of the gold in the older sediments came from underlying gold-bearing rock, via chemical and biological processes when the climate was humid. Subsequently, gold was transferred into younger sediments by the action of burrowing creatures, erosion and flooding, during the dry climate phase of the past few million years.

The samples from termite mounds and acacia leaves reveal that gold is preferentially absorbed by living material, and suggests that digging deep under gold-rich trees and mounds could lead to veins of gold.