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How are gold nuggets formed? From quartz vein to river

By Raquel · Updated 19 October 2026 · 4 min read

A nugget is the end of a story that lasts millions of years: it begins kilometres underground, in extremely hot water, and ends in river gravel or a few centimetres below the surface. Here it is, step by step.

The origin: hot water kilometres underground

Gold is very thinly spread through the Earth’s crust: on average there are only a few milligrams per tonne of rock. To concentrate it, something has to carry it: very hot, water-rich fluids that move through fractures several kilometres down and can carry dissolved gold. When those fluids change temperature, pressure or composition, the gold drops out of solution and is deposited.

It almost always ends up in cracks that fill with quartz: the gold-bearing quartz veins, or reefs. Studies of Australian nuggets show that their crystal structure formed at high temperature, deep underground, not at the surface.

The missing piece: earthquakes

For decades one question had no answer: if the fluids carry so little gold, how do accumulations large enough to make multi-kilo nuggets form? In September 2024, a team from Monash University in Australia, led by Chris Voisey and Andy Tomkins, proposed an explanation in the journal Nature Geoscience.

Quartz is piezoelectric: put it under stress and it generates a voltage. In the laboratory, the researchers shook quartz crystals immersed in a gold-bearing fluid, imitating an earthquake, and found that gold was deposited on the quartz. Their hypothesis is that, earthquake after earthquake, quartz acts like a natural battery and the gold already deposited like an electrode that attracts more gold. That would be how the large masses of gold in veins slowly grow.

Erosion sets the gold free

Over millions of years, rain, ice and temperature changes break down the rocks at the surface. When a gold-bearing quartz vein is exposed and weathers away, the gold, which does not oxidise, is released. If it stays near the vein, it forms what are called eluvial deposits: angular nuggets, often with pieces of quartz still attached.

Rivers: where placers are born

What does not stay near the vein is carried off by water. Gold is so heavy, about 19 times denser than water, that it settles as soon as the current loses strength: in cracks in the bedrock, on the inside of bends or behind large boulders. These deposits are called placers or alluvial deposits, and they yield most of the nuggets found with pans, sluices or detectors.

Tumbling along with the gravel, a nugget is knocked, bent and polished. That is why the further it has travelled, the rounder and smoother it usually is. Some studies also suggest that part of the gold in certain river nuggets may have been deposited within the placer itself, but most of the gold comes from the veins.

How to “read” a nugget

• Angular, rough, with traces of quartz: it has not travelled far from its vein. Common in Victoria’s Golden Triangle in Australia.
• Rounded, smooth and shiny: it has rolled a long way down a river. Typical of Alaska’s placers.
• Small and flattened: water has hammered and flattened it for a long time; common in fine river gold.
• Colour: natural gold almost always contains some silver, and the more silver, the paler it is. That affects its purity and value, as we explain in how much a gold nugget is worth.

Why every nugget is unique

No two nuggets are alike, because each one is the result of its own history: the vein it came from, the earthquakes that helped it grow, the distance it travelled and the knocks it took along the way. That is why natural nuggets are valued above their weight in gold, and why we like to photograph them in macro: every fold tells you something.

To learn about the three regions ours come from, read our guides to Alaska, Australia and Lapland.

Written by Raquel, Gold Nuggets Minerals

Raquel selects, weighs and photographs every nugget we sell. Gold Nuggets Minerals S.L.U. is a small company in Zaragoza, Spain, specialising in native gold. On Catawiki we have sold more than 120 nuggets, with 100% positive feedback and the Top seller badge.