Fire Assay

The most accurate precious metal assay

Fire assay – MGS Depending on lot size and expected turnaround, sometimes acid testing or X-RF testing isn’t the best assay option. In those cases, Manhattan Gold & Silver will suggest a fire assay.

Benefits of a Fire Assay

A fire assay – or melt test – is a complex precious metal assay that is commonly used at major mining companies and refineries. It’s accurate between one part per thousand and one part per ten-thousand – this makes it the most accurate assay method.

To perform a fire assay, the sample is melted and mixed with lead oxide and a few control chemicals. The lead in the mixture binds with the precious metal in the sample. The entire mixture is poured into a mold and cooled. Because the lead is so dense, it sinks to the bottom of the mold, where it is chipped off and placed into a cupel and melted again. The cupel absorbs the lead, leaving only precious metal behind. This is measured against the size of the rest of the sample to determine its overall purity.

When Will I Get My Results?

For a fire assay, we must send your sample offsite to be tested for a $25 fee. Although highly accurate, this precious metal assay takes time and you may not receive your purity results for a day or so. However, MGS keeps money on hand so you can be paid the very moment the results of your test are in. If you need a fast and highly accurate assay for a lot – large or small – contact us.