How gold refining works

What refining actually does

Karat gold is an alloy. A 9ct ring is 37.5 percent gold; the rest is copper, silver and zinc, added for hardness and colour. Refining separates the gold from everything else, so what comes out is fine gold: 999.9 parts per thousand. The base metals do not survive the process, which is why every honest refining deal is priced on the fine content of your lot, never its gross weight.

Step one: testing the lot

Before anything is melted, the lot is weighed and its composition measured, typically by XRF analysis. This matters more than any other step for you as the customer, because it fixes the number everything else is calculated from. A mixed bag of 9ct, 14ct and 18ct scrap has one meaningful figure: the grams of fine gold it contains. You should see that figure, and agree to it, before your metal goes anywhere near a furnace.

Step two: separating the gold

There are a few routes to the same destination. The most common for scrap lots is dissolving the metal in aqua regia, a mix of acids that dissolves gold, then chemically precipitating the pure gold back out of the solution while the base metals stay behind. Very low-carat material is often first alloyed with silver, a step called inquarting, so the acids can reach the gold properly. Where the target is the highest purity, 999.9, the metal is finished electrolytically. The chemistry varies; the outcome is the same: gold on one side, everything else on the other.

Step three: pouring the return

The refined gold is melted and returned as grain, small shot that a jeweller can weigh out for casting, or poured as a single bar. Grain is the practical choice if you plan to work the metal; a bar is the tidy choice if you plan to keep it.

How the fees work

This model is called toll refining: you keep ownership of the metal and pay the refiner a toll for processing it, rather than selling the lot to them. Fees are quoted as a percentage of the fine gold content. Ours is 15 percent, taken in metal rather than cash: send 50 g of 9ct scrap, which contains 18.75 g of fine gold, and 15.8 g of 999.9 gold comes back to you, with no invoice and nothing else to pay. The gold refining page has a calculator that shows the exact split for any weight and carat.

When refining beats selling

Refining makes sense when you want to keep the metal: a jeweller turning customer scrap back into casting grain, or someone consolidating inherited odds and ends into a single bar. If what you actually want is money, selling is simpler and faster: we buy gold outright at published prices per gram, paid by bank transfer. Our guide refine or sell? walks through the decision properly.