Assure Directory

LEO by Gemlogis/Jubilee Diamond

Instrument Description


The Leo was purchased by the Diamond Producers Association and tested by the independent laboratory UL on behalf of the Diamond Producers Association. ASSURE ID: 85689.


Leo is a portable desktop diamond verification instrument for loose and mounted stones. Leo is designed separate diamonds from synthetic diamonds and diamond simulants. Leo is manually operated but gives an automatic test result. Leo is suitable for an environment where you need to test both mounted and loose diamonds.


Instrument Specs

Size: n/a

Weight: n/a

Price: n/a

What Stones Can Be Tested?

Weight of stones: 0.01 ct-12 ct

Colour of stones: D-M

Diamond simulants: Yes

Jewellery: Yes, open back settings (please note this has not yet been tested by the ASSURE Program)


Capabilities according to Gemlogis’ website

Instrument Functionality

Automatically feed the stones? No

Automatically interpret the results? Yes

Automatically dispense the stones? No

Detect or refer synthetic diamonds? Refer

Detect or refer diamond simulants? Detect

Multiple stones at one time? No

Training? n/a

How Does it Operate?

The instrument tests individual stones and automatically displays a test result. The user manually places a loose or mounted polished stone into the LEO. To start the testing, the user closes the lid and presses the start button. LEO automatically presents the test result.

Leo displays one of the following results:


  1. Earth mined
  2. Type II
  3. Simulant
  4. Cubic Zirconium
  5. Moissanite


The “Type II” result could contain potential synthetic diamonds and diamonds. These referrals shall be tested by a gemmological laboratory for full verification.


Leo was tested in accordance with the Diamond Verification Instrument Standard with the test protocol for instruments that separate diamonds, synthetic diamonds and diamond simulants (Operation Category 3).


The tests took place at the independent laboratory UL in Canton, Massachusetts, United States.The tests were performed by a novice operator. Leo was tested with the ASSURE Core Sample.



The UL test summary report can be found here.


ASSURE Core Sample

The ASSURE Core Sample consists of 1,000 loose diamonds, 200 loose synthetic diamonds and 200 loose diamond simulants. The stones are 0.02 ct to 0.20 ct in D-J colour. The below results are from the test with the ASSURE Core Sample.


Diamond False Positive Rate Ratio of synthetic diamonds and diamond simulants incorrectly classified as 'diamond' to the total number of synthetic diamonds and diamond simulants 4.6%
Diamond Referral Rate Percentage of diamonds being referred for further testing 3.7%
Diamond Accuracy Percentage of diamonds correctly verified as 'diamond' 51.6%
Speed Stones tested per hour 219
Safety Testing

The most important requirement when selecting a Diamond Verification Instrument is that the instrument meets the safety regulations of your local jurisdiction. Before purchasing an instrument, request that the manufacturer verifies that their instrument complies with all regulatory requirements.


The ASSURE Program has no information about the safety credentials of the instrument.