Top Secret Gold & Silver Refining EXPOSED

Key Concepts

• Gold Refining: The process of removing impurities from raw gold to achieve high purity (e.g., 24 karat or 99.99% pure).
• Perth Mint Refinery: The facility where the gold and silver refining processes were filmed.
• Homogeneous Mix: A uniform mixture of gold, achieved by melting different batches together.
• LBA Accredited Referee Status Lab: An on-site laboratory with accreditation for precise analysis of gold purity.
• Primary Refining (Gold): An older method using chlorine, being phased out in favor of advanced melting units.
• Pyrometallurgical Advanced Melting Units (PAM): New machines that superheat gold to remove impurities, achieving 95-96% purity.
• Secondary Refining (Gold): An electrolytic process using a mixture of hydrochloric acid and nitric acid (aqua regia) to achieve 99.99% purity.
• Anode (Gold): A gold bar shaped for suspension in the refining bath.
• Cathodes (Gold): Sponge or sheets of pure gold collected at the bottom of refining cells.
• Gold Granules/Shot: Small pellets of pure gold produced by dripping molten gold into water.
• Gold Wire: Used to precisely adjust the weight of gold for casting bars.
• Graphite Molds: Used for casting gold bars.
• Silver Refining: A process that bypasses primary refining and goes directly to secondary refining.
• Anode (Silver): Silver bars shaped for the refining bath.
• Silver Nitrate Bath: A solution of nitric acid and silver nitrate used to remove impurities from silver.
• Silver Crystals/Dust: The final product of silver refining, in a crystalline or powdered form.
• LBMA (London Bullion Market Association): An international trade association for the London bullion market.

Gold Refining Process at Perth Mint

Gold Purchasing and Initial Assessment

The process begins with raw gold from mines, which can appear to have varying levels of purity. To ensure a consistent product, these different batches are melted together in a furnace to create a homogeneous mix. A sample of this molten gold is then sent to an LBA accredited referee status lab on-site for analysis. This analysis, which takes 12 to 24 hours, determines the exact percentage of gold. The refinery then balances this purity percentage with the weight of the gold after melting to negotiate ownership with the mine. This purchasing process is described as being very quick, with melting and sampling taking only a few hours.

A notable practice is that each mine is assigned its own dedicated pot, preventing the mixing of gold from different sources. The melting process involves extremely hot furnaces, requiring the use of a crane to handle the heavy gold bars (approximately 12 kilos each). Protective equipment is essential for workers, and filming was conducted from behind a protective glass window due to the intense heat. Molds used for pouring are preheated to prevent gold from popping out during the process, with a tray in place to catch any spilled bits. These spilled bits are then swept up and remelted, allocated to the original mine.

Primary Refining (Pyrometallurgical Advanced Melting Units - PAM)

The first stage of refining is called primary refining. While older methods utilized chlorine, these are being phased out. The new technology employs Pyrometallurgical Advanced Melting Units (PAM). These machines superheat the gold in a crucible, enclosed to boil off impurities. This process refines the gold to approximately 95-96% purity.

Secondary Refining (Electrolytic Process)

Before proceeding to secondary refining, the gold is melted and poured into a unique shape resembling a gift tag, serving as an anode. This anode is then suspended in a highly concentrated mixture of hydrochloric acid and nitric acid, heated to about 140° Fahrenheit. This aqua regia bath dissolves the remaining impurities, yielding gold of 99.99% purity. The video shows multiple refining cells in operation, with gold anodes suspended in the solution. The pure gold, in the form of cathodes (described as sponge or sheets), collects at the bottom of these cells. The resulting gold is refined to 99.996% to 99.998% purity, referred to as "four 9s fine gold."

Final Processing and Bar Production

Even at this high purity, the gold is not yet ready for coins or bars. A final step involves melting the gold one last time. It is then dripped into water, forming granules or shot. These granules are subsequently dried and collected in buckets. Each bucket can hold over 60 kilos of gold, valued at over $8 million.

The production of gold bars is a largely automated process. Robots load the pure gold shot into cups, slightly underfilling them to allow for the addition of gold wire. This gold wire is precisely cut to ensure the exact weight for 1-kilo gold bars. The cups are then automatically loaded into graphite molds. The same machinery is used for various bar sizes, including 1 oz, 5 oz, and 100g bars, by simply changing the mold size. A graphite lid is placed on the mold before the gold is melted one final time. After casting, the bars are stamped with their specifications and serial numbers, making them ready for sale.

Silver Refining Process at Perth Mint

Silver Purchasing and Secondary Refining

Silver arrives from mines in a raw form and, like gold, is melted down to determine its purity before purchase. Unlike gold, silver bypasses primary refining and goes directly to secondary refining. After melting and shaping into anodes, the silver is placed in a bath of nitric acid and silver nitrate. This solution dissolves impurities, leaving behind 99.99% pure silver.

Final Product and Bar Production

The refined silver, when pulled from the cells, is not in a sponge form like gold but is still described as visually interesting. It is washed and dried before being chopped up. The final product is silver dust or crystals, which the presenter humorously refers to as "pixie dust." This silver dust is collected in bins, which the refinery is in the process of upgrading.

The silver crystals are loaded into a hopper and then into a machine that produces 1,000-ounce bars, which are sent to places like the LBMA in London. The refinery also produces 1-kilo silver bars. While the 1,000 oz bars are largely automated, the 1-kilo bars require manual polishing before stamping.

Conclusion

The video provides a detailed, behind-the-scenes look at the sophisticated processes involved in refining both gold and silver at the Perth Mint Refinery. It highlights the technological advancements, stringent quality control measures, and the scale of operations required to transform raw precious metals into highly pure products ready for the market. The presenter expresses gratitude to the Perth Mint for the opportunity to film this exclusive process, which is not generally accessible to the public. A follow-up video is promised to showcase how the refined gold and silver are transformed into coins.