Discovering a gold nugget is lucky, but how much of it is actually pure, valuable gold?
Gold nuggets are pieces of larger gold ore deposits, known as lodes. As weathering breaks down the gold lodes in the ground, gold nuggets form. This process of ‘dissolving’ the gold lode into smaller pieces is the reason for the varied shapes and sizes of the nuggets.
This variation in gold nuggets can also be seen in the purity of each nugget’s total mass.
Composition of gold nuggets
Gold nuggets are not 100% pure gold.
In fact, gold nuggets are a metal alloy that can consist of a range of other metals, usually in trace amounts. These metals can include silver, copper, and nickel, as a few common examples. While silver is documented as being in most gold nuggets, trace amounts of palladium and iron are also very rarely found.
Although these other metals affect the purity of a nugget, gold is a ‘chemically stable’ metal. This simply means that gold does not combine with other metals very easily. Most nuggets found in nature are considered ‘pure’ and referred to as ‘native gold’. Historically, gold benefited from this natural purity by needing less or no refinement before being used or displayed.
So, gold nuggets are usually within a range of about 75% to around 95% pure. On average, nuggets found in Australia are very pure (around 85 – 95%), whereas Alaskan nuggets fall on the lower end of purity (around 75 – 85%).
These are the facts, but how exactly do we determine the purity of a nugget? There are a few things to know.
Measuring gold nuggets
The easiest way to tell how pure a gold nugget is without the use of a testing kit or smelting it down is simply by observing its color. Although not very accurate, the richer and brighter yellow or gold coloring, the higher the gold content will be.
There are two measurement systems which determine the purity of a gold nugget:
One karat is equal to 4.1667% or 1/24. In this case, one karat would be a single part of the whole mass of a nugget. So, a 22 karat gold nugget would be 22 parts (~91.6674%) gold and 2 parts (~8.3334%) of another metal. The karat value of gold is listed with a ‘K’ or ‘kt’ (22K/22kt).
Fineness as a measurement functions the same as karats. It represents the gold part of a mass with a value out of 1000. A nugget that is 75% (18K) gold would be labeled 750 fine. After being smelted, the fineness of the gold is often included in the bar mold.
Separate from purity, the ‘troy system’ is used to measure the weight of primarily gold and silver. It consists of the mass units: the grain (0.065 grams), the pennyweight (24 grains), the troy ounce (20 pennyweights), and the troy pound (12 troy ounces). Determining the weight of a gold nugget is necessary to figure out its total value.
Factors that affect purity
Even though you won’t be able to find a truly ‘pure’ gold nugget, depending on a few factors it will still be very valuable.
The geographical environment, or rather the specific lode that the gold came from, can cause unique alterations to the purity.
As weathering occurs the amount of other metals in a nugget decreases. Given enough time and movement, most impurities will leave a nugget.
This isn’t a consistent factor, however, smaller nuggets have less surface area for other metals to attach to. This can mean that the smaller a nugget is, the higher its purity may be.
Gold is one of the natural resources which you can rely on finding at high quality. Its natural appeal even in the form of a gold nugget is what makes gold prospecting so alluring. Anyone can discover a gold nugget with a bit of luck, experience, and knowledge.
If you are still interested in the world of gold nuggets or simply enjoyed this article, we encourage you to share it with anyone and comment about your thoughts.