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Diamond Authenticity


#1

I have a question about diamond testing… we had a diamond
that recently came into the store that tested as a diamond on
the standard electronic tester, but I was not convinced because;

  1. there was porosity on a poorly done retipping job and cracks
    in the metal, possibly indicating that the prongs might have
    been bent back and replaced by someone other than a jeweler…

  2. the stone, although lower in color, not perfectly round,and
    slightly chipped on the girdle, was absolutely clean looking
    under a loupe.

Is it possible that it is a YAG or some other synthetic that
tests as a diamond on a regular tester? I thought to put it to
the test with a torch, but would like to be sure of what to
expect before asking the customers permission.


#2

YAGs do not fool a diamond tester, but a Moisanite will if it is
an older tester (2yrs). The diamond testers rely on thermal
conductivity and unless there are user errors or a damaged probe
they are typically reliable. YAG and other simulants, except
for Moisanite, can not dissipate heat fast enough to fool the
tester.

Check for doubling. Moisanite is doubly refractive and will
split the images of facet junctions when viewed through the
crown facets to the culet.

Arthur


#3

The only material other than diamond that shows as a diamond on
the thermal diamond tester is moissanite (sp?).

Moissanite can be differentiated from diamond by looking,
through the table of the stone, at the facet junctions near the
culet with a loupe. Moissanite is doubly refractive, diamond is
singly refractive. A moissanite stone will show doubling of the
facet junctions, diamond won’t. You may have to look at several
of the facet junctions to see doubling if it is present.

Dave


#4

A low color diamond can most certainly be flawless (as a matter
of fact it is easier to get a low color flawless diamond than a
high color one!) and diamonds do sometimes chip on the girdle.
However, I always trust my gut instincts and if I think it isn’t
real , but my equipment all says something different, I’ll bring
it to some other gemologists or send it in to a lab. Don’t heat
it if you don’t know for sure what it is,.


#5
   Moissanite can be differentiated from diamond by looking,
through the table of the stone, at the facet junctions near
the culet with a loupe. Moissanite is doubly refractive,
diamond is singly refractive. 

C3 (mossainite manufacturer) is now cutting most of the material
on the C axis which means that you are looking through the only
singly reflective direction in the stone when you look through
the table (and you won’t see any doubled facets). However, as
someone else pointed out, look though the crown facets to the
culet and you will see doubling under magnification. If you try
and look at the table reflection when looking through the
pavilion, you will see it is also doubled.