Assaying

Assaying is how we put a number on purity — the figure a melt result, a refined bar or a bullion trade all get priced against. Our Sharjah laboratory runs a full complement of analytical methods on every lot, rather than defaulting to a single technique.

Methods

• Cupellation (fire assay) — the referee method, carried out to international ISO standards. A weighed sample is wrapped in lead and heated in a porous cupel; the lead and base metals oxidise and are absorbed, leaving a bead of precious metal that is parted and weighed. It is slow and destructive, and it is the figure settlement is based on.
• X-ray fluorescence (XRF) — rapid, non-destructive screening. A bar or sample is scanned in seconds, giving a first fineness figure and flagging plating, coatings or an unexpected alloy before anything is melted or dissolved.
• Atomic absorption spectroscopy (AAS) — a dissolved sample is analysed element by element, which is how we quantify the silver, copper and other metals that make up the balance of a lower-fineness lot.
• Potentiometry — an electrochemical titration used to determine silver content precisely, which matters for material where the silver fraction drives the value.
• Density testing — a physical cross-check of a bar’s specific gravity against what its stated fineness predicts. It catches plated or filled pieces and gross substitution without cutting the bar.

Sampling

For melted material the sample is drawn from the poured bar, not from the original scrap, so the assay measures the homogeneous batch that is actually being valued. Bars arriving whole are screened by XRF and density on intake, and sampled for fire assay where a referee result is required. Every sample is logged against the client and the lot before it enters the laboratory.

Turnaround and results

A standard result is issued within 24 hours, and the minimum sample size is 1kg. Where the lot is going on to refining or sale, the result becomes the figure that settlement is based on. We keep a record of the method used and the sample taken for every lot, and if you have a question about a result we will go through that record with you.

The assay certificate

Every result is issued as a formal certificate referencing the client and sample, the method used, and the measured fineness — the document a client’s own records, and any counterparty they deal with, can be checked against.

Why five methods

Most refiners in this market publish one or two assay methods. Running the full complement — a rapid non-destructive screen (XRF) alongside the referee-standard destructive method (cupellation), backed by atomic absorption spectroscopy, potentiometry and density testing — means the method can be matched to the material and the result cross-checked, rather than relying on a single technique for every lot.