Recently we've been asked by the Van Graff company (http://www.van-graff.com/) to do a review of their diamond simulants. In the interests of educating the public and finding out the facts, reknown appraiser Dave Atlas (http://www.gemappraisers.com/) and myself volunteered for the task. Here are the results of our findings.
First some tests and comments from Dave.
"I have done some testing
and the results are very pleasing.
There still is nothing quite
like diamond, but the Van Graff can fool the best trained folks in
gemology if they just use their eyes.
The Van Graff simulant that I
received was cut like an ideal cut diamond. Very nicely finished and as
bright, face-up as any or nearly diamond. Scintillation is similar and
dispersion is similar.
Compared to CZ there is no contest as you can
see, if the photo posts properly.
You probably can't tell which
stone is the Van Graff and which is the ideal cut diamond...
I had a real problem getting all three stones to be directly perpendicular to the camera at the same time. The stone in the center is the Van Graff and the stone on the right was the ideal cut diamond. The one on the left is the CZ.
The Van Graff that was sent to me was a flat out D color GIA and had no UV fluorescence. When one heats regular CZ they tend to get yellower in color quite rapidly. I am going to perform that test next on the Van Graff to see if it shifts in color upon exposure to heat compared to a CZ.
Here are two CZ's and a Van Graff BEFORE heating. 10 seconds with a butane torch and no protective coating.
10 seconds in a butane
flame torch without coating them for protection, two stones were heated,
One a CZ and one Van Graff. Both were damaged. The CZ turned very dark,
the Van Graff barely changed color. It appears the Van Graff would have
very good color stability compared to some CZ's.
As Dave collects more data I'll update his commentary and pics. Some other observations and comments by Dave which are equally important are this.
conclusion
I like the Van Graff product. It is an excellent diamond simulant,
face-up. It will fool nearly everyone who does not give it gemological
testing....
Consider using this as a viable substitute for diamond
when the budget demands restraint... No problem.
We need to see
this stone NOT referred to as SYNTHETIC DIAMOND, as it clearly is not a
diamond or a man made diamond.
I appreciate this opportunity to
provide you with honest advice..
Short of gemological testing or
looking from the pavilion side of the stone, I think very few experts
could detect anything unusual or not diamond-like in the appearance of the
Van Graff material.
I think it is a violation of the Federal Trade
Commission guidelines for a seller or manufacturer to use the term "Van
Graff Diamond". Maybe one could use "Van Graff simulated diamond"
or
"Van Graff imitation diamond". One could use the term "Van Graff", but I
do not believe it can be placed with the word "diamond" and not qualified
as "imitation", "simulated" or "fake".
I don't view that as a major
problem as the material speaks for itself very well. Undoubtedly proper
cutting is of major importance in providing this successful appearance. We
would hope all the stones will be cut this well.
I couldn't agree more with Dave's assessment. When the Van Graff simulants come loose they are sent in a sealed plastic stone holder against this back drop. This little "cert" has some interesting information to provide.
I think this is what caught Dave's attention and mine as well. I don't think it's appropriate to use the word "diamond" alongside anything unless it really is. My only suggestion here would be to change the wording to "Van Graff diamond simulant" as opposed to "Van Graff diamond" as the latter suggests a real "diamond".
(*Aclaratory Note: This was corrected and changed to "Van Graff simulated diamond" in the new certificates.)First thing I did upon receiving the Van Graff was put it under the microscope to see what we have going on there.
The gemstone did reveal minor imperfections similar to those found within a VS2-/SI1+ clarity diamond.
As observed in the picture above taken by Dave the stone is colorless. I ran the stone on my colorimeter to get this reading...
woops... left that graphic on the work computer .. hehe... this'll be updated. Just to let ya know the stone scored the highest color D possible. :) Even D color diamonds rarely *ever* get the reading this stone did.
The facets in this next pic fail to come to a "point". This is nothing to get alarmed about in a simulant. If it were a diamond however it'd be taking a serious hit in the department of symmetry.
As far as the pavilion mains lining up with the brother kite facets on the crown all checked out well here too.
This next report shows the girdle thickness all the way around the
stone as well as the length
of the star facets as they extend from the
table to the girdle. Most super ideal cuts on the market
have
star facets extending 55-60% to the girdle. These have shorter
stars. In the near future I'll
be putting together a report on
the effect of star facets and the other 40 mystery facets and how
they
affect the diamonds overall brilliance.
For you cut geeks ... here it is facet by facet. ;)
My internal analysis consists of 3 tests broken down into 5 components.
For those who are not familiar with the image below, here is the principal behind this image. The diamond has a white light source below it. A diamonds facets function either as windows or mirrors. Mirrors reflect light back at ya ... windows let light pass through it. The diamond is totally encompassed in the colors red & black. The black is actually a reflection of the eye (or camera) viewing the stone which is exactly perpendicular to the table of the stone, red is every other angle other than perpendicular. There are only 3 primary colors that can be observed with 2 secondary color. Red, black and white are the primary colors, the other 2 are pink (mixture of red and white) and gray (mixture of black and white). Interpretation ...
Red = light being return that is not perpendicular to the top of the
diamond
Black = light being returned perpendicular to the top of the
diamond
White = leakage
Pink = light being returned to the eye but
not as intensely as those that are darker red
Grey = light being
returned to the eye but not as intensely as those that are darker gray (or
black)
This first example is of a diamond that receives an AGS4 because of table size. As you'll note there are more intense reds than others, blatant areas of white in many places and a noticeable lack of internal symmetry.
Here's the Van Graff simulant.
Other Super Ideals under my IdealScope.
Note that there are no blatant white areas in the Van Graff
stone.
The stone reflects light back to the eye just as
beautifully as these super ideals.
This has to do with the alignment of the facets on an internal level and affects the beauty of a gemstone as well.
Here's an example of a Super Ideal Cut Hearts & Arrows diamond similar to what you'll find in my inventory.
Here's the Van Graff
Bottom line ... incredible internal symmetry for a CZ. Note that the arrows do not reach the ends of the stone due to the fact that the bezel facets don't quite point to the end (as noted above in external symmetry).
These results speak for themself. Bottom line ... I'm impressed. Next factor ... cost ... that's to come. :)
