Hello everybody,
Can I get some input on windows in faceted stones? How do they affect the value? I received a couple nice tsavorites both are over 3 carats, one described as IF and the other VVS They are brilliant in the pavilion, but the table has a window. I did the newspaper test and can see the print. On the plus side you can see how clean the stone is, but it lacks the luster the rest displays. I have another from a previous buy. It is slightly included with fingerprints only seem under a loop, but I think it looks better. I was planning on setting one in a ring and keeping the others for my collection or later settings.
Hello, I am so sorry to inform you that you may have purchased lab grown gems due primarily to the window under the table. As this happens in Manufactured gems.
If the stones are found to be natural and are of a good size, you might consider spending the money and having them recut. You would lose some ct weight, but I’d rather look at a smaller stone with sparkle and fire than a larger stone that looks like glass.
It doesn’t matter if the stone is natural or manufactured, a window indicates the stone has been cut at the wrong angles for that material and refractive index. It often occurs with overseas cuts as they cut for weight not brilliance, by having the stone professionally re-cut you will: 1. Lose weight, 2. Increase in value as the stone will exhibit greater brilliance and be far more marketable.
There is nothing worse, in my opinion, than a windowed stone, particularly one set in a nice piece of jewellery.
I sometimes buy windowed stones as I know I can re-cut them and get my money back plus!
A stone with a window cannot be called a “gemstone”, because it is not an actual finished “gem”. Windows are caused by the lack of knowledge in the field of faceting…or…a faceter that doesn’t care about the final product. Stones in different mineral families, have different refractive indexes, that is the angle a stone must be faceted at to properly reflect light. This reflecting light inside of a finished gemstone is what gives the gem its brilliance. A stone with a window means that a lot of light is simply passing through the stone and not being reflected back and out the table of the stone, making the stone loose a major amount of its brilliance, luster and sparkle.
Your stones have been cut too shallow for that material. The only way to fix that is to have the stone recut with the proper angles on the pavilion. That holds true for any material, man made or natural.
Taking the valuation process used by the Gemwold Guide as an example, I’ll outline how it works for tsavorite. The Guide would deduct a half a grade to one whole grade for the loss of brilliance which windowing causes. You would go from 70 to 100% brilliance with no window to a half grade less with a window that gave 60 to 70% brilliance or one grade less with a window that gave 40 to 55% brilliance. Since a window usually involves the area of the whole table, which is 50 to 60% of the stone’s area, it would be easy to go from 95% brilliance to 50%. Then you have to consider that the stone’s color is washed out by a window, so the color grade is affected, too. As an example, in a 3 to 5 ct stone, if you went from grade 8 to grade 6.5, your valuation would change from about $2,500/ct to about $2000/ct. Some criticise the Gemwold Guide for being too high, but I think the price difference would still be about the same, so about $500/ct…for a 3 ct stone, this is about $1500. Against this balance the loss of weight of about 10 to 15% to recut to no window. So loss of weight about $500 to $700, but gain in valuation, about $500/ct…$1500-$600= +$900. At the lower grades, the difference between grades could be just $200/ct or less and at the highest grades as much as $1800/ct. So for fine tsavorite, it would probably pay to have it recut. If I were to recut such a stone, I would use an apex crown if the stone were very shallow, so I wouldn’t lose too much weight. Recutting a stone might cost $100 to $300, so the net effect is still positive. I hope this info is helpful. -royjohn
Thanks Royjohn,
That is helpful and the information I needed. What is the best way to find an experienced faceter in my area? I live in the Dallas/Ft.Worth area. Also, how about GIA certificates? Do they add value, or peace of mind?
Cert adds peace of mind. Someone looking to make a major purchase or a highly valued stone to be cut would feel more relaxed with someone certified.
But I can bet you the best in the world arnt certified.
Think about it does gold lower in price if ur not a certified prospecter? Or certified gold Smith?
The quality and precision of cuts and polish. And also the style of cut is where you can loose value easily. And of course quality of the stone it’s self
There is a list of certified factors from competition from Novice to Grand Master available at https://usfacetersguild.org/certified-faceters-tp/. You may need to make further contact with the USFG to chase contact details.