The fineness of a precious metal object (gold coin, gold bar, gold rounds, etc.), represents the weight of fine metal in it. It also includes the base metals and/or other elements within that object. In jewellery, 'base metals' are added to increase both hardness and durability to the gold product. When talking about pure "24 karat" gold, however, what is the difference between 9999 and 999 fine gold? First, you need to understand how gold is measured.
Before Tackling 9999 vs 999 Gold, Let's Understand How it's Measured
There are two common ways of measuring the fineness of gold, the millesimal fineness scale and the karat measure. The karat measure is in-fact used only for gold (diamonds rely on carats with a "c"). In this article, I elaborate on these two scales. I discuss what pure gold actually is and when 9999 vs 999 gold makes sense from a buyer's perspective.
Millesimal Fineness vs. Karat
Millesimal fineness is a system of denoting the purity of platinum, gold and silver alloys by parts per thousand of pure metal by mass in the alloy. The karat is a fractional measure of purity for gold alloys, in parts fine per 24 parts whole. To the right is a comparison chart between the millesimal fineness and karat rating of common types of gold.
Breaking Down Gold Fineness
417 - 10 Karat - Gold that is 41.7% pure
585 - 14 Karat - Gold that is 58.5% pure
750 - 18 Karat - Gold that is 75% pure
916 - 22 Karat - Gold that is 91.67% pure
999 - 24 Karat - Gold that is 99.99% pure
999 vs. 9999 Fine Gold is All About Refining
Gold purity is determined post-refining and due to varying technologies and standards around the world, not everyone does it the same way. For instance, the minimum accepted fineness of gold around the world is 99.5%. As you can see in the corresponding table - 0.15 oz of gold per kilogram purchased is nothing to laugh at; at just US$1,200 per oz. it comes to US $180 per kg bar. Despite most European and North American clients expecting 99.99%+ purity, this is mostly a fact of the declining cost of refining, over time. That is to say, the difference between refining to 99.5% and 99.99% for most primary refiners is negligible compared to market preferences for a purer product. The challenge, as I explain below, is getting to 999.99%+ purity and above. This "five nine" metric is still widely used only on collectible products that sell for a significant premium to their intrinsic commodity value. While there are a few products still traded at purities lower than "995," these are generally limited to 98.6% Austrian Ducats and 91.7% British Sovereigns, Kruggerands, and US Eagles.
Refining 9999 vs 999 Gold: a Similar Story
According to the Royal Canadian Mint,
they employ a two-stage process. First, the Miller chlorination process, an industrial-scale chemical procedure, is used to refine gold to a high degree of .995 purity. Once you get to that standard, the Mint employs the Wohlwill electrolytic process. This process refines gold to 99.99%+ purity and can go to 99.999% and 99.9999%+ bullion and collectible coins. So where does the process begin? Refining starts with the reception of doré by the refiner. That's new product received from mines. In addition, primary refiners like the mint receive scrap such as jewellery and coins for recycling. The next steps are taking the semi-refined product containing at least half base metal and using that to produce fine metal.
Fact: there are really only two truly accurate ways that businesses can verify the fineness of gold they purchase. The first, naturally, is to melt it down and assay the metal. This is a somewhat costly process yielding a highly accurate result. The "fire assay" as it is known in the industry is considered the most reliable method for accurately determining the content of gold in a "lot." It also works for silver and platinum-group metals (PGMs). The second is to use an X-ray fluorescence (XRF) device that can also be used on the unmeleted product. In this case it only measures the outermost portion of the metal, but it does so relativly precisely. This machine has become a key component of most gold processing facilities (gold recyclers, refiners, or mining operations). The beauty of the XRF machine is that the concentration of gold can be determined somewhat near to a fire assay. Yet, it only takes a fraction of the time (seconds and not hours).
Refining to 995 Gold:
- Place the product into a crucible and melt it at a high temperature in a furnace while injecting chlorine gas into the molten metal.
- Remove the resulting by-product of chlorine and base metals (as well as silver) that forms at the top of the molten metal to get the 995 gold. Make sure to hang onto this "slag" and stockpile it to refine any trace amounts of gold at a future point.
- Cast the molten gold into anodes if you want to continue refining it, and otherwise into a saleable form.
Refining to 999+ Gold:
- Take the cast gold anode and place it into the appropriate acid-based electrolyte. Then set up a titanium cathode to attract the gold.
- Apply an electric current to the anode, dissolving the gold and other trace metals into the electrolyte and then attracting the gold to the charged cathode.
- Collect the gold that has formed around the cathode to cast into bullion product, and keep any trace elements that have settled for future gold recovery.
99.99 vs 99.999 Fine Gold
Fine gold is gold that is almost pure. As aforementioned, its purity is typically graded using a scale of millesimal fineness. As 100% pure gold is essentially impossible to achieve, the purest type of gold commercially available is 999.99. This is also referred to as five nines. The Royal Canadian Mint regularly produces commemorative coins from this fine gold. One example of a 99.999% gold product is the 30th Anniversary of the Silver Maple Leaf - 1 oz. Gold Coin (face value of $200).
Just below the five nines are the four nines - 999.9 fine. American Buffalo and Canadian Gold Maple Leaf coins are made from this fine gold. Most commonly, fine gold is 999. This is the gold most commonly referred to as 24 karat gold, although technically 24 karat gold is 100% pure. However, as this is difficult to achieve outside of a lab environment, 999 gold is considered close enough. Gold manufacturers are legally allowed a half-karat tolerance in making gold products. Fine gold is also known as three nines fine.
Below this is 995, the minimum amount allowed in Good Delivery gold bars. Two nines fine, or 990, is rarely seen, but technically a type of fine gold.
Pure gold has a bright yellow color, however, when mixed with other metals, white and rose gold are commonly produced. White gold is mixed with usually palladium or nickel to give it a color close to silver or platinum. Rose color gold is an alloy including about 25% copper, giving it a pinkish color. Because colored gold such as white or rose gold must be mixed with other metal, colored gold is never 'pure'. Therefore, colored gold is generally not considered 'fine gold' and used for jewellery as appose to bullion products.