The forces released by earthquakes exert sufficient force on quartz, a mineral present on Earth, to generate electric fields which in turn cause the formation of gold deposits.
Turning lead into gold. This is the dream of alchemists, who hoped to make a fortune and live forever, by means of the legendary and highly coveted philosopher’s stone. Discovering a link between quartz and the formation of gold, a team of Australian scientists are touching on this old fantasy that still permeates our imagination.
In an article published this Monday, September 2 in the scientific journal Nature geoscience, the researchers established that the forces released by earthquakes are capable of compressing quartz enough to generate electric fields, which in turn lead to the formation of valuable gold deposits.
While large gold nuggets tend to form underground, along fracture lines that cut through quartz, the reason for their formation was until now unknown.
A piezoelectric process
Recent laboratory experiments in Australia have shown that seismic waves produce electrical voltages strong enough in quartz to extract dissolved gold from fluids infiltrating the mineral.
Quartz, a mineral present in nature, has the particularity of being the only piezoelectric material abundant on Earth, that is to say which generates electrical energy when subjected to mechanical stress.
“This mechanism may help explain the creation of large nuggets and gold networks,” the study’s researchers say.
To test their hypothesis, Dr Christopher Voisey of Monash University in Melbourne and other Australian researchers immersed pieces of quartz in water in which gold had been dissolved. They then subjected the quartz to the stresses that rock experiences during an earthquake.
At the end of the experiment, they concluded that the deformations produced by the seismic tremors could generate sufficient electric fields in the quartz to extract gold from the solution surrounding it. Gold nanoparticles thus appeared on the surface of the quartz and others formed above it.
The Mystery of the Giant Nuggets
Scientists say the new discovery could explain why in some cases gold is extremely concentrated and forms very large nuggets. The World Gold Council estimates that between 2,500 and 3,000 tonnes of gold are mined each year. Most of the nuggets come from quartz veins, which account for about three-quarters of all gold ever mined.
“Understanding the mechanism of formation of these deposits can potentially help target rich gold deposits,” Dr Taija Torvela, a structural geologist at the University of Leeds, told The Guardian.
The only downside: to find these gold deposits, it is necessary to identify potential markers detectable on the surface of the Earth, “which this process would leave behind”, the scientist qualifies.
In March, the largest gold nugget ever discovered in England was unearthed by Richard Brock, a metal detectorist during a dig in Shropshire. The metal, dubbed “Hiro’s Nugget”, is worth £30,000, or more than €35,000.
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