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The Electrifying Secret Behind Giant Gold Nuggets
Context:
New research from Monash University suggests that the formation of gold nuggets in quartz veins may involve electrical processes. This new finding could change how we understand gold formation.
- Gold nuggets have long been the object of fascination and excitement, driving historic gold rushes and capturing the imaginations of treasure hunters.
Gold Nugget
- They are appreciated for their beauty and rarity. Each nugget is unique, with its shape, texture, and colour.
- Typically, it contains 75 to 97% gold, with the remainder mainly silver and sometimes inclusions of quartz.
- Nuggets with higher silver content appear whiter.
- Nuggets in jewellery are high purity, clean, shiny, and consistent, attractive.
- Traditionally, it was believed that gold precipitates out of hot, water-rich fluids as they move through cracks in the Earth’s crust.
- As these fluids cool or change chemically, gold separates and gets trapped in quartz veins.
- The World Gold Council estimates that between 2,500 and 3,000 tonnes of gold are mined annually.
- Most gold nuggets originate from quartz veins, which make up roughly three-quarters of all gold ever extracted.
Key Highlights:
- The research team investigated piezoelectricity, a property of quartz that generates an electric charge when stressed.
- This effect is seen in quartz watches and BBQ lighters, where a small mechanical force produces a notable voltage.
- Researchers hypothesised that earthquakes could induce similar piezoelectric effects in the Earth’s crust, potentially affecting gold formation.
- To test this hypothesis, researchers submerged quartz crystals in a gold-rich fluid and applied mechanical stress with a motor to simulate earthquake conditions.
- The stressed quartz not only electrochemically deposited gold onto its surface but also caused the formation of gold nanoparticles. Additionally, gold tended to deposit on existing gold grains instead of forming new ones.
- Gold’s conductive properties created focal points for further growth, effectively “plating” the grains with more gold.
Implications:
- The discovery indicates that quartz acts as a natural battery with gold as the electrode, accumulating more gold after each seismic event.
- This explains why large gold nuggets are often found in quartz veins associated with earthquakes.