Diamond Melee Screening: What a Supplier Should Document

Diamond melee screening examines small stones using methods designed to help distinguish natural diamonds from material requiring further investigation, which may include laboratory-grown diamonds, treated diamonds or simulants. The scope and meaning of the outputs depend on the method used.

GIA’s Melee Analysis Service addresses the separation of natural melee from laboratory-grown diamonds, simulants and potentially HPHT-treated natural material. Its published criteria currently include D-to-Z goods measuring 0.9–4.0 mm, with a minimum submission of 250 stones. These are criteria for that service, rather than universal limits for every screening method.

The documentation must therefore answer two questions: Was the method suitable for the goods, and can its results be connected to this shipment? Owning a screening instrument does not, by itself, answer either question.

Some screening instruments provide “pass” and “refer” outputs. A natural pass has a meaning within the instrument’s operating scope; a referral calls for further investigation. GIA’s 2024 review of laboratory-grown diamond identification explains that referred stones can be natural or laboratory-grown, and that users need to understand an instrument’s limitations.

Final identification resolves what the material is. Quality grading or sorting addresses other questions, such as colour, clarity and finish. IGI’s parcel sorting service describes quality ranges and additional parameters available on request, illustrating why the scope of each document matters.

A supplier should specify whether you are receiving a screening summary, further-testing results, a parcel quality assessment or a combination. Read Uniglo’s diamond certificate guide for background on laboratory documentation, then examine the actual document supplied for the melee.

Assign a lot reference that appears on the screening record, packaging and supply documents. Record the incoming weight in carats, the stone count where available, shape, size range and declared origin. State whether a count was measured or estimated; do not use an estimated count as though it proves every stone was processed.

The record should also identify the submitting party and the date of receipt or submission. For a supplier combining several purchases, retain the references to the incoming lots. This makes it possible to investigate discrepancies without relying on a generic product description.

Separate the declared origin from the test conclusion. “Submitted as natural diamonds” records the supplier’s declaration; “identified as natural diamonds” records a result within the stated scope. Treatment requirements should also be explicit when the order depends on them. A natural-origin conclusion alone should not be rewritten as proof of every other product claim.

Ask whether every stone was examined or only selected stones were tested. Record the submitted quantity, the quantity actually examined and any goods that could not be assessed. If several runs were needed, identify them and explain how repeated processing was handled without counting the same stones twice.

Sampling can provide information about the stones selected. It cannot establish the origin of every untested stone in a parcel. A supplier should describe sample-based work accurately rather than calling the whole shipment individually screened.

For all-stone coverage, ask how the operator checked that no goods remained in the input tray or were set aside without a result. A machine log showing a large number is useful only when its relationship to the submitted lot is clear. Equipment stops, unreadable results and handling exceptions should have a recorded outcome.

For in-house work, retain the instrument manufacturer and model, an equipment identifier and the applicable software or configuration information where relevant. Ask for the method’s documented size, colour, shape and mounting limitations. Where more than one method was used, identify the purpose of each.

The suitability check matters especially for unusual goods. IGI’s research announcement on fancy-colour identification explains how treatments can complicate screening and why colour-specific procedures may be needed. A method suitable for a colourless round parcel should not automatically be assumed suitable for every fancy-colour or mounted stone.

Request evidence supporting the chosen operating scope, such as the applicable instructions or a laboratory’s written service description. There is no need to demand publication of proprietary algorithms. The useful evidence establishes that the goods fit the method and that exceptions received appropriate handling.

For supplier-operated equipment, the internal record should identify the operator, screening date and procedure used. Retain any preparation requirements, operating checks and relevant maintenance or service status required by the equipment’s instructions. Do not invent a universal calibration schedule: the appropriate checks depend on the instrument.

For outsourced work, record the laboratory or testing provider, submission reference, service requested and result-document reference. Keep that document with the supplier’s lot record. A supplier’s use of a laboratory-designed instrument is different from having that laboratory perform the examination and issue the results.

Ask for a concise customer-facing summary backed by retained records. It can identify the responsible business and reviewer without exposing unnecessary employee details or confidential customer information. The point is to make the work accountable and explainable, rather than to collect an equipment photograph as a substitute for lot evidence.

Record the instrument’s original categories and their meanings, then document any further examination. Do not silently relabel “refer” as “lab-grown” or include unresolved referrals in a natural release merely because most other stones passed.

In a published GIA examination of a melee parcel, additional testing identified natural diamonds as well as HPHT-grown diamonds among the referred material. This is a specific laboratory case, rather than an estimate of contamination across the market.

For each referred group, retain a connection to the original lot, the provider or method used for further work, the final result and the disposition. Unresolved goods should remain distinguishable from released goods. For a natural-only order, agree that unresolved stones will be withheld pending identification, replaced or otherwise handled under the purchasing terms.

The record should explain where the submitted goods ended up. Account for the released quantity, goods identified as another origin or material, outside-scope stones, unresolved material and any handling discrepancies. Preserve measured weights and counts where available, with their units and measurement limitations.

Counts of repeated scans are different from counts of unique stones. Likewise, an initial referral is not an additional stone once its final result is recorded. A clear summary separates the initial screening stage from the final disposition so that the totals do not double-count material.

Assign responsibility for reviewing the record and approving the parcel for its stated purpose. A mismatch should be investigated before release. If only weight reconciliation is available, state that limitation; matching weights alone does not prove that the identical individual stones remained in the parcel.

Record the final lot reference, released quantity, date, packaging identifier and any seal reference. IGI’s published screening protocol describes natural diamonds returned in tamper-proof bags with the analysis date, seal number, result, parcel weight and customer reference. Those details provide a useful connection between the examination and the package received.

A seal supports that connection; its presence is not the whole test record. Check that the identifiers match the document. If the goods were repacked after laboratory return, the supplier should explain that step and provide the connection from the tested parcel to the package now delivered.

When lots are split, create references for the portions and record the quantities transferred. If goods are added, replaced or combined, establish appropriate verification for the new composition. A report for the earlier parcel cannot automatically cover stones added afterwards.

Use this template when setting purchasing requirements. Suppliers can meet it through a coherent set of records; every field does not need to appear on a single laboratory document.

Agree the records before purchase. This helps avoid discovering after delivery that the screening claim refers to an earlier shipment or only a small selection.

The following is a fictional record showing how the stages can fit together. It is not a laboratory report, a supplier performance claim or a typical referral rate.

Incoming lot: Example M-001, declared natural, 1,200 measured stones. Assume the selected method is suitable for the eligible goods and its documented pass supports natural identification within that scope.

The initial total is 1,170 + 20 + 10 = 1,200. The final disposition is 1,188 natural stones, two laboratory-grown stones and ten outside-scope stones, again totalling 1,200. The twenty referrals are replaced by their final outcomes in the final count, rather than added a second time.

For a natural-only release, the supplier could release the 1,188 supported natural stones after review while keeping the other groups separate. The ten outside-scope stones still need a suitable examination if they are later proposed for that order. Actual records should also account for measured weights and handling discrepancies.

If the accepted lot is split into portions of 600 and 588 stones, give each portion a reference linked to M-001. Adding twenty unexamined stones to either portion creates a new verification question; the original record does not answer it.

Send a parcel-specific request that the supplier can answer clearly:

Please provide the screening or identification evidence for the exact melee lot offered. Confirm whether every stone was examined, identify the testing provider or equipment and applicable scope, and explain any referrals, outside-scope goods or unreadable results. Please show how the final quantities reconcile and how the released parcel is linked to the supplied packaging. If it was split, repacked or topped up after testing, provide the relevant handling record and explain what verification covers the current goods.

At receipt, compare the identifiers before opening the parcel. Keep the invoice, screening summary, supporting results and any photographs of the label together. Raise a broken seal, missing reference or unexplained quantity difference before committing the goods to production.

Review coverage when the composition or identity of the lot becomes uncertain: additions from another source, undocumented mixing, lost labels, unexplained discrepancies or goods returned from production without clear identification. Confirm that new goods are covered before placing them in a screened inventory bin.

Opening a parcel for a documented split does not change diamond origin and does not automatically make the earlier testing worthless. The question is whether the handling records still support the connection to the tested goods. Decide what further examination is needed according to the gap in evidence and the purchase requirements.

For mounted jewellery, ask which components were accessible and examined. Do not assume a centre-stone report covers every accent stone or that an examination of accessible stones covers hidden material. Establish the provider’s actual coverage and any limitations in writing.

When reviewing Uniglo’s melee diamond parcels, include your origin, size and documentation requirements in the enquiry. Ask what lot-specific screening or identification evidence is available and how it connects to the parcel being offered.

Contact Uniglo Diamonds to discuss your requirements. A clear screening record helps your purchasing team assess the origin claim while your setter separately assesses fit, condition and matching.

• Natural vs Lab-Grown Melee: How to Compare Parcels
• What Are Melee Diamonds? A Buying Guide for Jewellers