Behind the scenes at The Perth Mint assay laboratory

Nov 15, 2022

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Two gold doré bars. Similar in size. Similar in weight. Apparently, however, very different in value.

How do I know?

Because the experts at The Perth Mint Refinery told me. And how do they know? Let’s find out.

It’s all about accuracy. Assay accuracy, to be precise. Because if the assay – the process used to determine the proportion of gold in these bars – is out by even the tiniest amount, that can clearly have a huge impact on your return.

And at The Perth Mint Refinery, the assay process starts right here, in the Melt House rough gold area, where your deposits are melted and electromagnetically stirred. This generates a uniform composition within the molten metal so that a truly representative sample is obtained.

And the remaining doré? That’s poured into bars which are kept safe and secure in The Mint’s central bank-grade vault until the refining process begins. Altogether, there are five samples taken. Three are sent to the lab and two are retained for independent customer and umpire analysis.

Now, as you can see, this is not your average lab. It is, in fact, one of the most advanced and best equipped precious metals assay laboratories in the whole of the southern hemisphere. And it’s home to a highly trained team of chemists and technicians with more than 200 years’ combined experience in precious metals analysis between them.

Your samples arrive in the receipts room by pneumatic tube. The X sample goes for preliminary X-Ray Fluorescence analysis. And the A and B samples? Their purity is determined by the Fire Assay. This dual stream analysis is conducted by two separate analysts to ensure the final result provides the greatest accuracy possible and to confirm we have obtained a truly representative sample of the melt.

Bullion analysis is a gravimetric technique that relies on high accuracy micro balances. These balances record the weight to one-millionth of a gram, with the newest balance reading ten-millionth of a gram. Needless to say, the whole process is highly involved, highly technical, highly skilled, and highly accurate. So accurate, in fact, that The Perth Mint Refinery’s gold analysis has been tested to be within 0.001 per cent for gold by the LBMA – the world’s premier regulatory body.

It’s this level of accuracy, and this uncompromising attention to detail, that you, as a producer, desire most. Because this is what determines your doré’s precise purity level. And it’s this, ultimately, that gives you your greatest possible return.

So, can you guess which one of these wins in the purity stakes? Actually, they don’t do guessing here.

Turns out it’s this one …. by 2%.