For centuries, gold nuggets, often found within quartz veins, have captivated treasure hunters and sparked gold rushes around the world. However, the mystery of their formation has intrigued scientists just as much. Recent research from Monash University has brought a fresh perspective, suggesting that the process of gold nugget formation might be more electrifying, quite literally, than previously thought.

Monash University’s Groundbreaking Research

Led by Dr. Chris Voisey from Monash University’s School of Earth, Atmosphere, and Environment, the study, which is soon to be published in Nature Geoscience, challenges the traditional understanding of how gold nuggets form. "The usual explanation is that gold precipitates from hot, water-rich fluids as they move through cracks in the Earth's crust," explained Dr. Voisey. He continued, "These fluids cool or undergo chemical changes, causing gold to separate out and get trapped in quartz veins."

While this widely accepted theory explains much of the gold found in nature, it does not fully account for the formation of large gold nuggets, especially given the low concentration of gold in these fluids.

Introducing Piezoelectricity: A New Perspective

The research team explored a novel concept known as piezoelectricity. Quartz, the mineral often found hosting gold deposits, has the unique ability to generate an electric charge when stressed. This property, known as piezoelectricity, is familiar in everyday items such as quartz watches and lighters, where mechanical stress creates a voltage. The researchers hypothesised that similar stresses, such as those caused by earthquakes, could trigger a comparable process within the Earth.

To test this theory, the team conducted an experiment simulating the conditions quartz might endure during an earthquake. They submerged quartz crystals in a gold-rich fluid and applied mechanical stress, mimicking seismic activity. Upon examining the quartz samples under a microscope, the results were remarkable.

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Stunning Results: Gold Accumulation Under Stress

"The stressed quartz not only deposited gold electrochemically on its surface, but it also formed and accumulated gold nanoparticles," noted Professor Andy Tomkins, a co-author of the study. Interestingly, the gold tended to deposit on existing gold grains rather than creating new ones. This behaviour is linked to the fact that while quartz is an insulator, gold is a conductor. Once gold begins to accumulate, it effectively "plates" itself with more gold.

Dr. Voisey added, "Our findings offer a plausible explanation for the formation of large gold nuggets in quartz veins. As the quartz undergoes repeated stress from seismic activity, it generates piezoelectric voltages that reduce dissolved gold from the surrounding fluid, causing it to deposit over time."

The Interplay of Earth’s Forces

This new understanding positions quartz as a natural battery, with gold acting as the electrode. Over many seismic events, this process could lead to the gradual formation of significant gold accumulations, producing the massive nuggets that have long fascinated both treasure hunters and geologists.

This study not only illuminates a long-standing geological mystery but also underscores the intricate relationship between Earth's physical and chemical processes. As scientists continue to explore these connections, our understanding of natural phenomena, such as gold nugget formation, will undoubtedly deepen, revealing even more of the Earth's hidden secrets.

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