Introduction
The screening methods described elsewhere in this section — UV fluorescence, cross-polarized light, microscopy, spectroscopy, DiamondView imaging — are designed primarily for individual loose diamonds of significant size. But some of the most pressing identification challenges in the diamond trade involve stones that are much smaller and often already set in jewellery.
Melee diamonds — typically under 0.20 ct, often under 0.10 ct — are the small accent stones in halos, pave settings, channel settings, and side-stone arrangements. They are purchased in parcels of hundreds or thousands and set by the batch. Individually, each stone is worth very little. Collectively, they represent a significant portion of the diamonds in any jewellery display case.
The challenge: how do you screen thousands of tiny diamonds efficiently, including stones already mounted in rings and earrings? The answer lies in purpose-built screening instruments.
The Trade Concern
Undisclosed lab-grown melee mixed into natural diamond parcels is not a theoretical risk — it is a documented industry issue. Because melee stones are traded in bulk at low individual values, they are vulnerable to mixing. A parcel of natural melee containing even a small percentage of undisclosed lab-grown stones compromises the integrity of every piece of jewellery those stones enter.
The economic incentive is straightforward: lab-grown melee costs a fraction of natural melee. Substituting even a few per cent of a natural parcel with lab-grown stones increases the seller's margin without any visible difference to the buyer. This is why melee screening has become a critical quality control step for responsible jewellers and dealers.
GIA iD100
What It Is
The GIA iD100 is a compact desktop instrument designed for bench-level diamond screening. It was developed by the GIA specifically to address the practical need for rapid, reliable screening in retail and trade settings.
How It Works
The iD100 uses a probe that is placed in contact with or very close to the diamond. The instrument combines spectroscopic analysis with proprietary algorithms to deliver one of two results:
- "Pass" — the stone is natural diamond
- "Refer" — the stone requires further laboratory testing (possible lab-grown or simulant)
Key Capabilities
- Speed: Approximately 2 seconds per stone
- Size range: Screens diamonds as small as 0.9 mm in diameter (~0.005 ct)
- Mounted stones: Can screen diamonds already set in jewellery, including prong, bezel, and pave settings — without removing the stone
- No expertise required: The pass/refer output is unambiguous. No spectral interpretation is needed from the operator.
Real-World Performance
In documented testing, the iD100 achieves high accuracy in separating natural diamonds from lab-grown and simulants. In a reported test of 100 melee side stones, the instrument referred 1 stone for further testing — demonstrating both sensitivity (it catches potential lab-grown) and specificity (it does not flag naturals excessively).
De Beers AMS2
What It Is
The Automated Melee Screening device (AMS2), developed by De Beers Group, is a high-throughput batch screener designed for the diamond sorting and manufacturing trade.
How It Works
The AMS2 processes loose melee diamonds in bulk. Stones are fed through the instrument, which performs automated spectroscopic screening on each stone and sorts them into "pass" and "refer" channels.
Key Capabilities
- Throughput: Up to 3,600 stones per hour
- Size range: 0.003–0.20 ct (approximately 1.3 mm to 3.8 mm diameter)
- Batch processing: Designed for screening entire melee parcels, not individual stones
- Automated sorting: Stones are physically sorted into pass and refer streams, ready for further handling
Use Case
The AMS2 is positioned for diamond sorting houses, manufacturers, and large-scale dealers who process significant volumes of melee. It is the standard tool for screening incoming melee parcels before stones enter the manufacturing pipeline — ensuring that any lab-grown or simulant stones are identified before they are set into jewellery.
Yehuda Sherlock Holmes
What It Is
The Sherlock Holmes, developed by Yehuda, is a portable diamond screening device designed for bulk testing of both loose and mounted diamonds. Now in its fourth generation (Sherlock Holmes 4.0), it uses independently verified technology validated through the Underwriters Laboratories (UL) ASSURE Testing Program.
How It Works
The Sherlock Holmes analyses diamonds through their fluorescent and phosphorescent characteristics under UV light. Rather than testing stones one at a time with a probe, the device illuminates an entire tray of diamonds simultaneously and captures the UV response. HPHT lab-grown diamonds typically exhibit strong blue phosphorescence that distinguishes them from natural stones, while CVD lab-grown diamonds show anomalous fluorescence colours. The operator interprets results through colour-coded visual indicators, with smartphone integration for image capture and comparison.
Key Capabilities
- Bulk screening: Tests multiple stones simultaneously — no need to touch each diamond with a probe
- Mounted stones: Accommodates up to 27 rings on the testing tray with rotating holders, allowing screening from all angles without removing stones from settings
- Loose stones: The 4" × 6" (10 × 15 cm) testing surface holds approximately 250 carats of loose diamonds
- Detection scope: Identifies HPHT and CVD lab-grown diamonds, as well as CZ and moissanite simulants, including diamond-coated imitations
- Accuracy: 100% lab-grown detection rate with a 2.5% false-positive rate (among the lowest of tested screening devices)
- Digital records: Cloud storage for test results with photo and certificate upload, supporting traceability and audit trails
Use Case
The Sherlock Holmes is suited for retail jewellers, dealers, and buying offices that need to screen mixed inventory — loose parcels and finished jewellery — without the throughput demands of a large sorting house. Its bulk-testing approach makes it particularly efficient for screening estate jewellery and second-hand pieces where individual stones cannot easily be removed for testing.
Gemetrix
What It Is
Gemetrix, an Australian manufacturer, produces a range of compact UV screening instruments designed for diamond and gemstone identification. The product line includes models optimised for different screening scenarios — from individual loose stones to mounted jewellery and melee parcels.
How It Works
Gemetrix instruments use dual-wavelength UV illumination at 254 nm (short-wave) and 365 nm (long-wave) to observe fluorescence and phosphorescence reactions. The operator compares the colour and intensity of fluorescence under each wavelength — a short-wave response stronger than long-wave, for example, is suggestive of synthetic origin. Results are captured and compared through the Gemetrix smartphone app.
Key Models
- PL-Inspector — a portable desktop unit (approximately 300 g) with a 15 × 15 mm inspection zone, optimised for individual loose stones. Battery or mains powered, making it suitable for trade events and travel.
- Jewellery Inspector — a larger-format version with a 50 × 50 mm inspection area, designed for testing mounted jewellery and bigger stones without removal from settings.
- Melee Inspector — purpose-built for screening small stones up to 0.40 ct each. Uses 255 nm short-wave UV to expose potential synthetics in bulk, with smartphone-based result capture for fast processing of multiple stones simultaneously.
Use Case
The Gemetrix range offers an accessible entry point for screening, with portable form factors and smartphone integration that suit independent jewellers, travelling buyers, and small-to-medium trade operations. The Melee Inspector fills a practical niche for businesses that screen smaller melee parcels without the throughput requirements of industrial-scale instruments like the AMS2.
Other Screening Instruments
Beyond the devices detailed above, several other instruments serve screening functions:
- GGTL ScreenMaster — a desktop screening device used in various markets
- De Beers DiamondSure — an earlier-generation screening instrument still in use in some facilities
- Various portable UV/spectroscopic devices — smaller, less expensive instruments that provide basic screening capability for field use
The market for screening instruments continues to evolve as the need for accessible, rapid lab-grown detection grows. Screening devices and diamond testers from multiple manufacturers are available through specialist suppliers such as arete.tools.
Best Practices for the Trade
The diamond industry has converged on several best practices for melee screening:
- Screen all incoming melee parcels before accepting them into inventory — regardless of the supplier's reputation
- Screen before setting — once melee stones are mounted, individual testing becomes more difficult and time-consuming
- Document screening results — maintain records of screening for each parcel as part of quality control and due diligence
- Re-screen estate and second-hand pieces — jewellery from unknown sources may contain undisclosed lab-grown stones
- Treat "refer" results seriously — a referred stone is not confirmed lab-grown, but it must be tested further before being treated as natural
- Invest in appropriate equipment — the range of available instruments means there is a screening solution for every scale of operation, from a single-store jeweller to a large sorting house. Diamond testers and screening devices are available from specialist suppliers
Relevance for Consumers
While screening instruments are trade tools, their existence protects consumers:
- Ask your jeweller about screening practices. A responsible jeweller should be able to explain how they verify the origin of diamonds in their inventory, including melee.
- Graded centre stones are already screened. If your centre diamond comes with a GIA or IGI report, it has been identified and documented. Melee side stones, which typically do not come with individual reports, are where screening practices matter most.
- Jewellery appraisals may include screening. Some appraisers now incorporate basic screening as part of their evaluation, particularly for estate and second-hand pieces.
- Industry education is expanding. Arete Diamond organises AreteWorkshop events for the jewellery community, where professionals and enthusiasts learn about screening techniques, grading practices, and the latest identification tools.
Frequently Asked Questions
Can the GIA iD100 test a diamond in a ring?
Yes. The iD100 probe can test diamonds mounted in most jewellery settings, including prong, bezel, and pave. The stone does not need to be removed.
How fast is melee screening?
The GIA iD100 screens individual stones in approximately 2 seconds. The De Beers AMS2 processes up to 3,600 loose melee stones per hour in batch mode. Both are fast enough for practical trade use.
What happens to stones that get a "refer" result?
Referred stones are sent to a gemological laboratory for advanced testing — typically spectroscopy and DiamondView imaging. The refer result means "investigate further," not "confirmed lab-grown."
Is melee screening expensive?
The instruments represent a significant range in price, from portable UV screening devices like the Gemetrix PL-Inspector to high-throughput batch screeners like the De Beers AMS2. The per-stone screening cost is minimal regardless of instrument — especially compared to the reputational and financial risk of selling jewellery with undisclosed lab-grown melee. For retailers, the iD100 and Sherlock Holmes are practical options. For high-volume operations, the AMS2 provides scale. Portable instruments like the Gemetrix range offer an accessible starting point for smaller operations.
Can undisclosed lab-grown melee really end up in natural diamond jewellery?
Yes. This is a documented industry concern. Lab-grown melee is visually indistinguishable from natural melee and costs a fraction of the price. Without screening, there is no way to detect substitution. This is why the trade has adopted routine screening as best practice.
Summary
Mounted and melee diamond screening addresses the practical challenge of identifying lab-grown diamonds among the small accent stones that populate most diamond jewellery. The GIA iD100 provides rapid, bench-level screening of individual stones — including mounted diamonds as small as 0.9 mm — in approximately 2 seconds. The De Beers AMS2 offers high-throughput batch screening for loose melee parcels at 3,600 stones per hour. The Yehuda Sherlock Holmes screens multiple mounted and loose diamonds simultaneously using fluorescence and phosphorescence analysis, while the Gemetrix range offers portable, smartphone-integrated UV screening from individual stones to melee parcels. Together with responsible sourcing practices, these instruments protect the integrity of the natural diamond supply chain and give consumers confidence that the stones in their jewellery are what they are represented to be.