Verifying the origin of mounted diamonds has become a difficult yet important undertaking for the jewellery industry. Laboratory-grown diamonds are prevalent. Identification can be hard. Combine these factors with the often small sizes of stones and the limited testing options due jewellery settings – it is enough to challenge even the more experienced of jewellery professionals.
The ARI by Presidium has been created specifically to help with this task. This portable handheld instrument is easy to use, gives straight-forward results, and can identify whether a diamond is natural, or whether it requires further analysis. It can also identify the trickiest of diamond simulants; synthetic moissanite..
• Mounted and loose facetted stones Diamonds, laboratory-grown diamonds and synthetic moissanites
• Colour: Colourless (D – J)
• Size: 0.02ct + Approximately 1.7mm in diameter
• Shape: Round brilliant cut and some fancy shapes.
• Cut quality: Very good +
• Simulants: Can identify synthetic moissanite only
The ARI works by analysing light reflected from the pavilion of facetted stones. Designed as a probe, the user simply places the probe tip at 90° to a stone’s table facet. The user initiates the test by pressing the probe carefully onto the surface. This triggers UV light to be shined into the material. Partial absorption of this UV light may occur as it passes through the material. Sensors in the base of the equipment analyse any light that is returned from the stone. Results are assigned by the ARI based on whether specific absorption features were detected in the returned light. An automated result will show up on the ARI’s digital screen within 3 seconds of testing.
List of possible results:
‘Diamond’ for natural diamond
Up to 98% of natural diamonds will gain this result.
‘Type IIa / HPHT / CVD’ for all type IIa diamonds
This includes a small percentage of natural diamonds and all colourless laboratory-grown diamonds. All stones that gain this result will require further tests and observations to determine origin.
‘Moissanite’ for synthetic moissanite
This includes the low-electrical conductivity synthetic moissanites.
The ARI is quick and easy to use, similar to generic diamond testers, and stones can be tested quick succession without a decrease in accuracy.
It is important to note that the accuracy of the ARI’s results relies on light that has been totally internally reflected by the stone. Therefore, reliable results are most likely obtained from well-cut stones. This test works best for well-cut round brilliants. Fancy-shapes may obtain unreliable results depending on the shape and proportions of the stone.
Assessment by the ASSURE Testing Program by the Natural Diamond Council has found that the ARI has a 6% false positive rate. This means that 6% of the stones that gained a ‘natural’ diamond result were incorrect. So, although this equipment will guide you right most of the time, it is recommended to use the ARI alongside other tests and observations.
Helpful tips from Julia:
• Use a diamond tester, such as the Presidium Multi Tester III (PMuT III), to screen out the majority of diamond simulants before testing with the ARI. Use the ARI on all stones that gain both a ‘diamond’ and ‘moissanite’ result. This is necessary as some laboratory-grown diamonds test as ‘synthetic moissanite’ and some synthetic moissanites that test as ‘diamond’.
• Use the ARI multiple times on each stone. If the result is consistent – I have found it to be a reliable result. If the results change every couple of tests – I have found this to be an unreliable result.
• Always perform further tests and observations on stones that gain a ‘Type IIa / CVD / HPHT’ result as well as those that gain an unreliable result. The stone could be a diamond or a laboratory-grown diamond. Assessing UV reactions is an excellent method for identifying the majority of origins. If further tests and observations cannot be performed, send the piece for testing at a gemmological laboratory.
• Only use the ARI on stones inside the recommended parameters to ensure accuracy.
The ARI by Presidium provides a good initial test when determining the identity of a colourless facetted stone. Priced at SGD1,749.00 (approx. £1015.00 GBP), the ARI by Presidium is considered one of the more affordable diamond screeners.