Imagine the earth rumbling deep underground, not only shaping new fold mountains, but also silently forming nuggets of pure gold.These huge chunks stored in museums, which can weigh up to 60 pounds, owe their existence to the shaking of the Earth, which causes the metal to shimmer and sway in a water-like liquid, possibly turning it into actual gold.

Earthquake or natural gold factory?

A new study published in Nature Geoscience suggests that earthquakes play a key role in the formation of giant gold nuggets by charging electricity to quartz-rich veins. This extracts the molten gold from the hot fluid, forming a solid metal over time.Gold deposits often form during mountain orogeny or the folding process of the Earth’s crust, where mineral-laden fluids seep through cracks in the Earth’s crust. These liquids contain tiny traces of gold, less than 1 milligram per kilogram of water, but create nuggets that can be filled by hand.

But how can such a small amount of metal aggregate into so much metal?

Crystals are the magical ingredient behind the magic. Although it is chemically inert, it binds very tightly to gold in the folded deposits of the Earth’s crust, areas that are hit by earthquakes when plates collide.Quartz has unique properties because it is strongly piezoelectric, making it the only mineral abundant in the Earth’s crust that generates an electric charge when placed under mechanical stress. According to a study in Nature Geoscience, when seismic waves repeatedly compress crystals within veins, this action increases the voltage.

Researchers tested this in the lab

Researchers at Monash University tested this by deforming quartz in a gold-laced liquid, reproducing conditions similar to earthquakes with compression and shaking.The researchers used the model to extend their findings to real quartz veins deep in the Earth’s crust. The stress from the earthquake generates an electric field that triggers an electrochemical reaction that forms gold nanoparticles on the surface of the quartz.

Quartz slows down this initial buildup because it is an electrical insulator. But when a thin metal film is grown, it acts like a conductive wire. “Dissolved gold tends to accumulate in pre-existing grains, turning initial patches into favorable growth centers during subsequent earthquakes,” the authors explain in Nature Geoscience.

How do these gold specs become big nuggets?

In an active fault zone, slips occur thousands of times, causing the cracks to reopen and allowing new pulses of mineral-rich fluid to flow in, simultaneously re-stressing the crystals.Each earthquake deposits additional layers of gold, forming an interconnected network that mirrors that observed in natural samples. According to the study, “the shimmering mass…is a frozen record of repeated seismic stresses in an ancient mountain range” and is not the product of a single fluid influx.