Nothing stoked the imagination of the 19th century public more than the idea of a remote, crystal-clear river peppered with glittering gold nuggets. And with good reason too; gold nuggets are nature’s depository of raw, unrefined riches. Their organically sculpted lines and warm metallic radiance are aesthetically pleasing at a primal level.
Gold is an extremely rare element, having an occurrence in the earth’s crust of approximately 3.1 parts per billion by weight. Gold ore from modern mines contains only microscopic specks of the noble metal; the contained gold is completely invisible to the naked eye. In fact, an open pit mining operation that yields just 2 grams of gold per ton of ore extracted is considered a rich mine.
Yet natural gold nuggets easily exceed even this remarkable rarity. It is estimated that only 3% of gold mined today is from alluvial (river) deposits. Most of this gold is in dust or flake form with only a minuscule fraction recovered as nuggets.
In addition, gold nugget discovery rates have been steadily declining by 5% to 10% every year for at least the last 30 years. This is despite considerable improvements in mining, dredging and metal detector technology during that time. Simply put, gold nuggets are nature’s winning lottery tickets and they are getting scarcer every year.
We normally think of nuggets as smooth, water-worn lumps of gold. And this is definitely the case when a nugget has been subjected to decades or even centuries of pounding hydraulic action in a swiftly flowing stream. However, not all natural gold nuggets have been through such harsh alluvial conditions.
Some examples possess well defined edges, almost giving them the appearance of crystallized honey. A few rare specimens even reveal gold’s marvelous cubic crystalline structure. Australian nuggets, often found in dry regions, sometimes display this intriguing, crystallized honeycomb look.
They typically range from 20 to 23 karats (83% to 96%) fine gold with primarily silver and small amounts of copper as alloying components. These trifling purity variances among nuggets generally have minimal impact on pricing. As a point of reference, gold nuggets are substantially finer than 14 karat (58%) or 18 karat (75%) gold used in higher end jewelry.
Australian gold nuggets are also renowned for their extremely high purity, commonly possessing finenesses in the mid 90% range. All of these factors combine to make natural gold nuggets from Australia highly collectible.
The Alaska/Yukon geographic area is the other great gold nugget region of the world. Natural gold nuggets from Alaska tend to be more water worn than their Australian brethren due to Alaska’s wetter climate. Alaskan nuggets also trend towards slightly lower purities than Australian nuggets, with finenesses commonly in the high 80% range. The slight differences in purity between Alaskan and Australian nuggets do not significantly impact desirability or pricing, however.
Although Australia and Alaska/Yukon are currently the two major global producers of gold nuggets, certain other historic gold mining districts are nugget rich as well. California, in particular, is inexorably linked with gold in the popular imagination. While large nuggets are rarely unearthed there today, small to medium sized nuggets are still found.
Sometimes gold is found still attached to its parent (matrix) rock. Quartz, with its characteristic milky-white, sugar-crystal appearance, is the most frequently encountered matrix material. Quartz has traditionally been a key indicator to astute prospectors that gold is nearby. The other matrix rock commonly found associated with gold is laterite, an iron-rich mineral that is a rusty red or blackish color. Laterite infused nuggets are commonly of Australian origin.
Gold nuggets that have experienced significant weathering or alluvial action typically have either little or no matrix. Due to their tremendous rarity, gold specimens prominently embedded in their matrix can be very expensive. Attractive examples sell for far higher premiums over bullion value than comparable gold nuggets with little or no matrix.
While all gold nuggets are natural works of art, some are more captivating than others. Larger nuggets are not only more impressive than smaller sizes, but also much scarcer. For example, a 16 gram gold nugget is estimated to be almost 5 times rarer than its 4 gram counterpart. Consequently, only gold nuggets of more than 2 grams in weight should be considered for investment purposes.