*Updated Sept 19, 2019
If you are in a hurry
Watch the video below to quickly understand what 999.9 means on gold.
(I made this video to function as a short summary of the article below).
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Companies carrying high-purity gold products have “999.9” or “999” stamped on their bars, coins or jewellery.
So, what does “999.9” mean on gold?
Also, occasionally you will see “24 Karat” or “24 K” stamped somewhere as well. More often you will find “24 Karat” mentioned in a product description though.
Both, “999.9” and “24 Karat” mean the same thing. It means that gold is virtually at its maximum fineness or very close to being 100% pure gold.
“999.9” and “24 Karat” are examples of two different systems used to show the fineness of gold (aka gold purity).
Although in the past there were more than several methods to indicate the purity of gold, these two systems are still used today.
Intuitively, you probably have a general idea what “999.9” means, so let’s start with this first.
The two systems are analogous. So, once you fully understand the meaning of “999.9”, you will better understand what “24 Karat” means (which I will discuss in the next post).
Meaning of “999.9” on gold
“999.9” or “999” are examples of purity representation of gold using millesimal fineness system.
In this system, fineness or gold purity is expressed in parts per 1000. In other words, it tells how many parts, out of 1000, are pure gold (in a given piece of gold).
To make it clear, picture a piece of gold that is broken down to 1000 parts of equal mass. Then, if all parts of pure gold (containing only 100% pure gold) are counted, you will get a purity in millesimal fineness.
For instance, a gold bar with purity of “999.9” would have 999.9 parts that are pure gold. The remaining 0.1 parts would be some other metal. It can be copper, silver, nickel, zinc or a combination of these. Because other metals make a given piece of gold less pure, sometimes they are called impurities.
Mathematically speaking, there is no such thing as 100% pure gold. But the purity can be pushed very close to 100%.
The higher the purity of gold, the closer the millesimal fineness gets to 1000. The vise versa is also true. The lower the purity of gold, the further the number gets from 1000 (and closer to 0).
Of course, in real life nobody breaks gold in 1000 parts. Instead, to get gold purity in millesimal fineness, the percent of gold (in decimal form) found in a given piece of gold is simply multiplied by 1000.
So, let’s say, you got lucky and found a gold nugget that is 0.78 gold.
To express the purity of this nugget in millesimal fineness, you multiply 0.78 by 1000 which equals 780. So, the purity of your gold nugget is 780.
**Keep in mind that once gold leaves refinery its purity has already been determined. For your info, gold refineries process raw gold taken out of the ground into pure gold.
I find it interesting that raw gold just taken out of the ground typically has the purity of at least 750 if expressed in millesimal fineness.
Does above explanation clear mud for you when looking at the “999.9” stamp? If not, let me know what’s not clear!
And until next time when I’m going to talk about the meaning of “24 Karat”.
I want to start exchanging paper money for 999.9 gold money