The formation of gold nuggets in quartz veins, although it may not seem so, has been a subject of debate for decades, especially because these deposits do not always follow uniform patterns. In many deposits, gold seems to concentrate in specific points, a characteristic that is not easily explained by the most widespread hydrothermal models.
The scientific community has been looking for alternatives to understand how metal-enriched fluids end up creating discrete accumulations in areas subject to seismic stress. In this context, in 2024, an international team used laboratory experiments to analyse the response of quartz to tectonic stresses.
How could earthquakes favour the appearance of gold nuggets?
The authors of the aforementioned study, published in Nature Geoscience, developed a model that relates the piezoelectric stress generated by quartz during an earthquake to the formation of gold nuggets.
It is important to clarify that quartz is a mineral capable of producing an electric field when subjected to sudden geological stresses. These conditions usually occur in regions where active faults allow the circulation of fluids that transport dissolved gold from deep zones of the Earth’s crust.
The study argues that when a seismic wave packet passes through a quartz-rich vein, the mineral can generate enough stress to alter the distribution of gold contained in the fluids.
Gold tends to precipitate at points where it encounters surfaces that facilitate nucleation, and this is where the piezoelectric electric field can play a decisive role. This mechanism would explain why accumulations are not distributed homogeneously, but appear concentrated.
The hypothesis is also consistent with the geological observation that many of the largest orogenic deposits show repeated episodes of fracturing and hydrothermal circulation. Each earthquake not only fractures the rock but also reactivates the transport and precipitation process, allowing gold nuggets to increase in size.
How does quartz piezoelectricity and gold nugget deposition work?
The team at Monash University (Australia) conducted an experiment in which they immersed quartz crystals in a fluid containing dissolved gold.
They then reproduced seismic waves to induce rapid stresses in the crystals. This stress generated a piezoelectric voltage capable of triggering the deposition of gold on the surface of the quartz, forming nanoparticles.
According to the researchers, these nanoparticles could be the starting point for the creation of larger gold nuggets. The very presence of adhered gold acts as an electrode where more metal is deposited in subsequent events.
One of the authors explained: ‘Gold dissolved in solution will tend to deposit preferentially on pre-existing gold grains.’ This dynamic suggests that gold nuggets grow through a cumulative process linked to successive seismic events.
The repetition of earthquakes facilitates new phases of deposition. In each cycle, quartz subjected to stress generates an additional charge that reorganises the dissolved gold, allowing the consolidation of interconnected metal structures. Over time, these accumulations give rise to the large fragments that are often found in fractured quartzite veins.
Repeated formation and growth of gold in seismic veins
Researchers have identified two keys to understanding the concentration of gold in active veins: the piezoelectric nature of quartz and the orogenic character of the deposits where the largest gold nuggets appear. Earthquakes not only open new pathways for fluids, but also induce stresses capable of activating the mineral.
This scenario creates a geological cycle that can extend over thousands of years.
Hydrothermal fluids rise through fractures, carrying small amounts of gold that end up adhering to crystals or already metallised surfaces.
Each earthquake generates new electrical conditions that promote accumulation. Over time, gold nuggets can reach significant sizes, as has been recorded in orogenic deposits in different regions of the planet.
Laboratory experiments have confirmed that the piezoelectric stress of quartz is sufficient to precipitate gold from aqueous solutions. In addition, they have proven that the solidification of the metal concentrates around pre-existing gold, reinforcing the accumulative mechanism.
This evidence supports the idea that the most voluminous deposits are the result of multiple interconnected seismic events.
Scientific implications of this discovery
One of the most talked-about aspects of the 2024 study is its potential to recreate gold nuggets under controlled conditions. The authors explained: ‘It’s not alchemy; you need dissolved gold and conditions for it to go from a liquid state to adhering to a surface.’
Although the procedure does not involve generating gold from scratch, it opens the door to a better understanding of its transitions within the geological cycle.
Unfortunately (for enthusiasts), the study does not offer a direct tool for locating deposits with gold nuggets. The detection of piezoelectric signals allows quartz veins to be identified, but does not confirm the presence of metal inside them.
