How Do Gold Nuggets Form? Earthquakes May Be the Key

Scientists have finally solved a long-standing mystery about the geologic process behind these large pieces of gold found in quartz rock. From a report: Gold has always been a hot commodity. But these days, finding a nugget isn’t too tricky: Much of the world’s gold is mined from natural veins of quartz, a glassy mineral that streaks through large chunks of Earth’s squashed-up crust. But the geologic process that put gold nuggets there in the first place was a mystery. Now, a new study published today in Nature Geoscience has come up with a convincing, and surprising, answer: electricity, and earthquakes — lots of them.

Those nuggets owe their existence to the strange electrical properties of common quartz. When squished or jiggled, the mineral generates electricity. That drags gold particles out of fluid in Earth’s crust. The particles crystallize out as grains of gold — and, over time, with enough electrical stimulation, those grains bloom into nuggets. “If you shake quartz, it makes electricity. If you make electricity, gold comes out,” says Christopher Voisey, a geologist at Monash University in Australia and the lead author of the new paper. Earthquakes are the most likely natural source of that shaking, and the team’s lab experiments show that earthquakes can make gold nuggets.

The idea that gold nuggets appear because of electricity instead of a more conventional geologic process is, at first, a peculiar thought. But “it makes complete sense,” says Thomas Gernon, a geoscientist at the University of Southampton in England and who was not involved with the new work. Quartz veins host a disproportionate number of gold nuggets and their environments experience plenty of earthquakes.