Australian gold nuggets?
Nuggets are large masses of gold found in soil and streambeds, known broadly as alluvial deposits. While nuggets have been found on many goldfields around the world, those from Victoria were particularly large and abundant. From the time of the first gold rush in the early 1850s, the discovery of a large nugget generated such excitement that news spread far and wide. Thousands of people from around the world migrated to Victoria, dreaming of making their fortunes on goldfields dripping, so they hoped, with nuggets.
How many nuggets were there?
No one knows how many nuggets were found. During the late 1800s, the Mines Department compiled an official list of discoveries and also made models of some of the large nuggets. By the time the reporting system ceased in about 1910, 1300 nuggets over 20 ounces had been recorded. However, almost certainly many more nuggets were found than were recorded, as many discoverers avoided publicity for fear of being robbed. None of the large nuggets found during the gold rushes survived, as all were quickly melted down. Today, fossickers with metal detectors still find large nuggets – those that the original diggers missed – on the Victorian goldfields.
How did Australian nuggets form?
While there are several theories for the origin of nuggets, the evidence points conclusively to them coming from the gold-bearing quartz reefs. Many big alluvial nuggets contain lumps of quartz, or show imprints of quartz crystals enclosed by the gold as it crystallised in cavities in the reefs. Why large masses should suddenly crystallise is not completely understood. However, it has something to do with conditions in the surrounding rocks changing the solubility of gold in the warm water that had dissolved it in huge amounts and carried it up from deep in the crust.
In some goldmines, large slugs of gold were found where quartz reefs cut particular layers in the surrounding sedimentary strata. These layers became known as ‘indicators’ and were actively sought out by the early miners. Over millions of years of erosion, the landscape was worn down, exposing the quartz reefs and the enclosed gold. Gradually, weathering caused the reefs to disintegrate, freeing the lumps of gold. These moved into the soil, then down slope into the nearest stream.
How pure is the gold in Australian nuggets?
Victorian nuggets are rich in gold, with most being at least 95% gold, or about 23 carats. The remainder is mostly made up of silver dissolved in the gold. The composition of the nuggets is very similar to the composition of gold found directly in the quartz reefs.
The Welcome Stranger, found near Moliagul in 1869, is the biggest known nugget, containing 2300 ounces of gold.
The Welcome, from Bakery Hill at Ballarat in 1858, contained 2200 ounces. The 1743-ounce Blanche Barkly, found at Kingower in 1857, the 1600-ounce Precious, found near Rheola in 1871, and the 1110-ounce Viscount Canterbury, found in 1871, also at Rheola, were other big finds.
In the 20th century, the largest known nugget found with a metal detector was the Hand of Faith, containing 870 ounces, from Kingower in 1980.
Australia produces about 300 tons of gold annually, currently ranking it about fourth in the world. Exploration for gold continues to be a major activity for Australian mining companies, with target areas extending to the South Pacific and Southeast Asian regions. Whether a discovery is ever mined depends greatly on the size and nature of the deposit and its geographic position, the concentration of gold in the rocks (known as the grade) and, perhaps most importantly, on the international price of gold. Despite some rich deposits being brought into production, none have changed the course of a nation like the fabulous finds of the 1850s. Credits: By Dr Bill Birch, Senior Curator, Geosciences, Museum Victoria