A replica of the Welcome Stranger, a gold nugget weighing almost 100 kilograms found in Australia in 1869
Ian Dagnall/Alamy
Earthquakes may cause gold nuggets to form in quartz by generating an electric field that attracts gold dissolved in fluid forced up from deep underground.
Enormous gold nuggets are often associated with quartz, a ubiquitous but chemically inert mineral. The world’s largest gold nuggets can reach weights of nearly 100 kilograms, but until now no one has been able to explain how such valuable lumps of metal were formed.
The Role of Quartz in Gold Nugget Formation
“The mystery has been how do you make a large gold nugget in a single spot when there’s no obvious chemical or physical trap,” says Chris Voisey at Monash University in Melbourne.
Voisey and his colleagues have now discovered a possible mechanism. When quartz is subjected to pressure, it produces a voltage that attracts gold that is dissolved in water. Quartz’s unique crystal structure plays a crucial role in this process.
Exploration of Gold Concentration Mechanism
Gold-bearing hydrothermal fluids from Earth’s mid to lower crust, 15 to 20 kilometers below the surface, are driven up through fissures during seismic activity. However, the concentration of gold in these fluids is extremely low, requiring a large volume to produce significant deposits.
Voisey’s team hypothesized that gold is concentrated into nuggets within veins by the piezoelectricity of the quartz during repeated earthquakes. Experimental work showed that gold deposition on quartz increased when subjected to pressure, further supporting their hypothesis.
Enhancing Gold Attraction
By coating quartz samples with iridium to enhance their piezoelectric response, the team observed larger gold deposits compared to uncoated samples. This phenomenon was attributed to the preferential bias for gold in solution to deposit on pre-existing gold, creating a self-reinforcing cycle of gold attraction to the quartz.
A replica of the Welcome Stranger, a gold nugget weighing almost 100 kilograms found in Australia in 1869
Ian Dagnall/Alamy
Earthquakes may cause gold nuggets to form in quartz by generating an electric field that attracts gold dissolved in fluid forced up from deep underground.
Enormous gold nuggets are often associated with quartz, a ubiquitous but chemically inert mineral. The world’s largest gold nuggets can reach weights of nearly 100 kilograms, but until now no one has been able to explain how such valuable lumps of metal were formed.
The Role of Quartz in Gold Nugget Formation
“The mystery has been how do you make a large gold nugget in a single spot when there’s no obvious chemical or physical trap,” says Chris Voisey at Monash University in Melbourne.
Voisey and his colleagues have now discovered a possible mechanism. When quartz is subjected to pressure, it produces a voltage that attracts gold that is dissolved in water. Quartz’s unique crystal structure plays a crucial role in this process.
Exploration of Gold Concentration Mechanism
Gold-bearing hydrothermal fluids from Earth’s mid to lower crust, 15 to 20 kilometers below the surface, are driven up through fissures during seismic activity. However, the concentration of gold in these fluids is extremely low, requiring a large volume to produce significant deposits.
Voisey’s team hypothesized that gold is concentrated into nuggets within veins by the piezoelectricity of the quartz during repeated earthquakes. Experimental work showed that gold deposition on quartz increased when subjected to pressure, further supporting their hypothesis.
Enhancing Gold Attraction
By coating quartz samples with iridium to enhance their piezoelectric response, the team observed larger gold deposits compared to uncoated samples. This phenomenon was attributed to the preferential bias for gold in solution to deposit on pre-existing gold, creating a self-reinforcing cycle of gold attraction to the quartz.
