By Michelle Graff
The AMS device developed by De Beers’ International Institute of Diamond Grading&Research shoots stones out into one of five bins: pass, refer, refer Type II, non-diamond and purge, for when the user needs to abort the current test and starLafayette, La.--Sightholder and supplier Stuller Inc. is one of two United States companies now using De Beers’ Automated Melee Screening device, which is designed to tell small lab-grown diamonds from natural ones. 

Stanley Zale, Stuller’s vice president of diamonds and gemstones, said Monday that the company purchased one of the machines and received it two weeks ago. While Stuller did consider using the machine to test stones for their retail customers, the company has opted to use it only for its own inventory. 

Stuller began running melee through the AMS device right away and, so far, hasn’t found a single lab-grown diamond among the thousands of stones it’s scanned, Zale says. 

He says the same is true for the HRD D-screening the company has been doing for years on diamonds 20 points and larger to check for synthetics. This process allows Stuller to detect if a diamond is Type IIa, which is rare in nature but common among lab-grown diamonds, and send it to a grading laboratory for further testing if so. 

To date, none of those diamonds have come back as lab-grown either, though Zale says having the HRD D-screening and AMS device are necessary today. “This is an insurance policy for the integrity of our business,” he says. 

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De Beers began deploying its AMS device in early July to sightholders around the world. Mumbai-based Kiran Gems along with Tasaki and Rosy Blue in Japan are among those companies using the machine. De Beers could not release the name of the second U.S. company to have one of the AMS devices by press time. 

The AMS device screens stones between 1 point (1.3 mm) and 20 points (3.8 mm) in size, automatically feeding the stones table-down into a testing station and then dispensing them into separate bins indicating if they pass (are natural diamonds), need further testing, or are not diamonds at all. 

It takes up to 500 carats of colorless or near-colorless melee at a time and scans one stone every 10 seconds. The cost of the AMS device, which can be left to run unattended, is $55,000 plus a three-year, $10,000-a-year support and maintenance charge, according to De Beers. 

Stanley said in receiving the machine from De Beers, Stuller also receiving a set of statistical sampling guidelines for testing melee--i.e., for every “X” number of carats of melee, run “X” percentage through the machine--noting, “You cannot check every stone. It’s not reasonable. It’s not realistic.”  

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