The Shor Fire Assay System

A process dating back thousands of years, in 1979 Shor introduced the first turn key in-house fire assay systems to the jewelry industry. These first systems purchased from Shor in 1979 are still in continuous use and will probably continue to be used well into the 21st century.

The method known as "Fire Assay" is the oldest known method of assaying gold and continues to be the most accurate and economical method of determining the purity of gold. Capable of precision down to 1 part in 10,000 the fire assay system allows you to make up to 20 assays at once with a cost as low as $1.00 per assay.

This system can easily and inexpensively be expanded to greater capacity. Every sample can be assayed for gold content, platinum & silver content. The process returns the sample as 999.99+% pure metal. Many samples can be assayed at the same time. We have separate procedures for both large and small batch sampling.

The assaying system will fit onto a 3' x 5' (90 x 150 cm) table and includes all equipment and supplies (except acid and water).

The Shor Fire Assay System comes complete with both written instructions that are updated regularly and the transcript of a seminar given by Shor on assaying (including questions and answers).

Additional technical support is available over the phone, internet and/or fax at no extra charge.

A brief description of how fire assay works:

The sample of gold is weighed very precisely and the amount is recorded. The sample is wrapped in assay lead foil along with a quantity of pure silver. This wrapped ball is placed in the furnace in a cupel (a special kind of disposable crucible). All the non-precious metals are absorbed by the hot cupel. The precious metal forms a button within the cupel. The cupel is removed from the furnace, from the cupel and then brushed to remove any lingering bits of cupel. It is hammered flat, rolled thin and then heated in a porcelain crucible containing a weak nitric acid solution. The acid removes the silver, which is poured off and the silver recovered from solution. The gold is then rinsed in distilled water to remove any residual acid and then dried. The sample of gold is now at least 99.999 pure. The sample is then weighed again. The original weight of the impure sample is divided into the weight of the now pure sample. The result is the assay