Moissanite is often being sold with inflated diamond equivalent weights. How to check:

Discussion in 'Moissanite Forum' started by talk-admin, Jun 27, 2017.

  1. talk-admin

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    Staff Member

    Apr 4, 2002
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    Hi all,
    I wanted to post on a troubling trend we have been seeing with a lot of Moissanite being sold with inflated diamond equivalent weights, and how you can protect yourself by understanding an easy to use formula to pretty accurately calculate the actual diamond equivalent to roughly +/- .01ct (and see if you've already overpaid for air).

    Background: As previously noted, in March we purchased a number of F1 and Moissanite round cut stones and had them all independently graded at NAGL. The original point of that was to investigate their claim of their regular and H&A rounds having 58 facets was true. As already discussed it was not - they all are 57 facet rounds meaning that for whatever reason, they are falsely claiming their round are 58 facets when they are not.

    Problem (besides the false claims about 58 facets): However, it was noted that the majority of Moissanite were all 'underweight' relative to what was claimed for diamond equivalent size, sometimes by 10%+.

    All of the gems were evaluated at the gem lab using the precise volumetric equivalent, the same as how Amora Gem is certed, which is the most precise way to determine diamond equivalent weight.
    ( To be fair, the smaller amount were overweight but usually minimally - i.e. not by nearly the % of underweight, and a much smaller % of how much overweight. )

    Example of inflated diamond equivalent - a 9mm F1 H&A that was sold as a "3.00"ct was in fact a 2.71ct diamond equivalent under volumetric measurement. That's a difference of .29cts, or greater than 10% of it's actual diamond equivalent weight. In other words, you are paying for 10% air. (Note- even Charles and Colvard will tell you a 9mm is 2.70ct).

    And more concerning to us, is someone comparing pricing on a 3ct Amora (a true 3ct) to a "3ct" F1 (but really 2.70sh carat) would make it look like the Moissanite was so much cheaper. That's legally unfair competition.

    For reference, all Amora Gems are certed using the volumetric equivalent for diamond equivalence. However, most jewelers and indeed some gems labs (esp one that certs a lot of Moissanite) don't have this equipment (requires an OGI HD, Sarin HD or Helium system to do it) and thus simply put what the seller tells them the diamond equivalent is (!).

    After extensive testing, here's how you can use to easily and readily compute the approx diamond equivalent of almost any Silicon Carbide (F1, Moissanite, Amora, etc) gem and see if you are really getting the diamond equivalent size the seller is claiming:

    Scale weight (weight of the gem on a scale) * 1.101 = Diamond Equivalent Weight (usually within ~ +/- .01ct).

    Here's an example of how to do it.

    The scale (or actual weight) is either on the cert, or can be weighed at your local jeweler.
    Then simply take that carat weight and multiply by 1.101. The result is a pretty accurate measurement of it's diamond equivalence, usually within plus or minus .01ct (accuracy may vary a bit but it's going to be very close). All Silicon Carbide is 50% carbon, 50% silicon, the difference is in the ordering, so you can leverage that and that's why this formula is pretty consistent across types.

    To do this on a cert, we can use this example posted on a moissanite seller's site:
    scale-weight-dew.jpg The scale weight (actual weight) is 2.08ct.

    The claimed DEW, or diamond equivalent is 2.50ct. Is that correct?

    2.08ct * 1.101 = 2.29ct.

    Thus, the actual diamond equivalent carat weight is most likely 2.29ct, and possibly 2.28ct or 2.30ct (plus or minus .01ct).

    As a result what is being sold as a 2.50ct is almost certainly 2.29ct, and thus .21ct or 9% inflated...or you are paying for 9% air as you think you are buying a 2.50ct but getting a 2.29ct instead.

    How can a cert have the wrong diamond equivalent weight, off by as much as 10% or more? Easy, the lab doesn't have the equipment to do a volumetric measurement and eliminates liability by putting this:


    In other words, the diamond equivalent is not something the lab determined.
    Rather, they simply put what the seller told them to!

    (And I will note- we provided this formula to this lab, privately, to let them know they were putting out inflated weights. They told us they "no longer wished to do business with us" even after they originally expressed interest in having a formula to check their work).

    And that's how you get rampant inflation of diamond equivalent weight, and a lot of moissanite being sold for larger than it is since no one is checking the DEW claims.

    You can use this scale weight * 1.101 formula to easily and quickly verify claimed diamond equivalent weights and see if it's in the ballpark - and thus protect yourself when reviewing any future Silicon carbide purchases (and evaluate past purchases and see if you can get a refund for over-payment).

    Hope that helps,

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