Aureus Africa Gold Guide

How Gold Assay Actually Works

Assay helps establish the precious-metal content of a sample. For a buyer, the important questions are not only which instrument was used, but whether the sample represented the whole lot, who controlled it and how the result connects to the material being purchased.

Follow the Process Product & Purity Guide

Identify the lotKnow exactly what is being tested

Sample correctlyMake the portion representative

Use a suitable methodMatch testing to the decision

Verify the reportConnect results to the shipment

Gold sample being prepared for independent assay

Start with the Right Question

An Assay Tests a Sample, Not a Sales Claim

A result such as 999.9, 916 or 750 describes measured gold content under the stated method and conditions. It does not by itself prove ownership, lawful origin, available quantity or that the tested sample came from the offered lot.

That distinction is especially important for doré, nuggets, dust and other material that may vary across a batch. Even an accurate laboratory result can mislead a buyer if the sample was selected from only the richest-looking portion.

Buyer principle

Treat sampling, testing and chain of custody as one verification process. A certificate without a traceable connection to the material is not enough.

Six Practical Stages

From Offered Lot to Usable Result

The exact procedure depends on product form, quantity and commercial agreement, but a defensible process normally addresses each stage below.

Define the Lot

Record the product form, count, gross and net weight, packaging, markings, seal numbers and other identifiers before sampling begins.

Agree the Sampling Method

Choose a procedure capable of representing the lot. Bars, molten doré, nuggets and fine material require different approaches.

Prepare and Split Samples

Homogenize where appropriate and create sealed portions for the buyer, seller and an independent umpire laboratory if required.

Maintain Chain of Custody

Record who handled each sample, when it moved, where it was stored and whether seals remained intact.

Perform the Analysis

Use a qualified independent laboratory or refinery and a test method appropriate to the product and commercial decision.

Review and Settle

Check identifiers, units, uncertainty and results, then apply only the pricing and tolerance terms agreed in the contract.

Testing Methods

XRF and Fire Assay Serve Different Purposes

A professional verification plan may use more than one method. Buyers should understand what each result can and cannot establish.

X-Ray Fluorescence (XRF)

XRF provides rapid elemental analysis and is useful for screening. It commonly measures the tested surface, so plating, surface enrichment, preparation, calibration and uneven composition can affect how well it represents the interior or whole lot.

Fire Assay

Fire assay is a destructive laboratory technique widely used to determine precious-metal content in a representative sample. Its strength does not remove sampling risk: a precise result for an unrepresentative sample remains unsuitable for valuing the full lot.

Density and Electronic Tests

These methods may support preliminary screening of suitable solid objects. Shape, voids, alloy composition, coatings and equipment limitations mean they should not automatically replace laboratory analysis for significant purchases.

Refinery Settlement Assay

Bulk or doré transactions may use refinery sampling and analysis for final settlement. Contracts should define provisional results, permissible differences, umpire procedures, payable content, charges and the result that becomes final.

Reading the Certificate

What a Buyer Should Check

A report should be read as transaction evidence, not decoration. Confirm its authenticity directly with the issuing laboratory when verification is available.

Laboratory or refinery name, physical location and contact or verification channel.

Report number, issue date and the exact sample or lot identifier.

Sample condition, preparation procedure and analytical method used.

Reported elements, purity units and whether results are percentages, parts per thousand or another basis.

Weight basis, uncertainty, detection limits or qualifications relevant to interpretation.

Signatory or authorization details and evidence that the report has not been altered.

Interpreting Purity

Convert the Result into Fine Gold Content

Fineness expresses gold in parts per thousand. Contained fine gold is estimated from verified net weight multiplied by verified fineness.

Illustrative example—not a product offer

If a representative sample supports a fineness of 850 and the verified net lot weight is 10 kg, estimated contained fine gold is 10 × 0.850 = 8.5 kg. The commercial payment may still reflect agreed payable percentage, refining losses or charges, taxes and other legitimate transaction terms.

Warning Signs

Pause the Transaction When Evidence Breaks

Photographs Presented as Proof

Images of bars, nuggets, instruments or certificates cannot establish current possession, internal composition or connection to an offered lot.

Seller-Controlled Sampling Only

A buyer should question samples chosen, handled and transported solely by a party whose payment depends on a high result.

Mismatched Identifiers

Names, weights, dates, seals, bar numbers and report references should connect consistently across the material and documents.

Pressure to Pay Before Verification

Urgency, exceptional discounts or claims that independent testing is unnecessary should trigger enhanced caution.

Assay FAQ

Questions Serious Buyers Should Ask

Does XRF prove a gold bar is solid gold?

Not necessarily. XRF is valuable for elemental screening, but the tested surface may not represent the interior. The verification plan should reflect the object, risk and transaction value.

Is fire assay always final?

Only when the parties have agreed that the result, laboratory and sampling procedure determine settlement. A contract should also address differences between laboratories.

What does 999.9 mean?

It normally expresses 999.9 parts of gold per thousand, equivalent to 99.99% gold under the reported test basis. The specific item and report must still be verified.

Who should pay for testing?

That is a commercial decision. The parties should agree costs, laboratory selection, witnesses, transport, split samples and consequences of an out-of-specification result before testing.

Can one assay certificate cover repeated shipments?

A report ordinarily relates to its identified sample or lot. Later material requires its own traceable verification unless a technically sound, agreed programme states otherwise.

Prepare a Qualified Enquiry

Discuss Product and Verification Requirements

Tell us the product form, estimated quantity, destination, intended use and preferred independent assay process. Availability, documentation and transaction terms must be confirmed for the particular enquiry.

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