General question about faceted colored gemstone ovals and windowing....

[matt_k]

A recent acquaintance who was in the fine jewelry business for over 30 years had THIS to say about ovals:

"Technically, all ovals have issues with brilliance and at least some windowing. No way around that. It’s the angles of the cut getting the length and width to come to a viper or keel line."


First off, this convo is waaaaay above my pay grade when it comes to the technical aspects of gem cutting. Haha. But it seems to have the ring of truth to it, after a fashion. I would love to hear what the hardcore "cut nuts" on this site have to say about the matter, however. Would you folks agree (more or less) with the above statement? And if so, could you elaborate a bit further on the difficulties and trade-offs in connection to producing a quality faceted oval? And which (in your opinion) is harder to produce: a quality faceted oval diamond... or a quality faceted colored gemstone?

Also: assuming that even quality faceted colored gemstone ovals all have a slight windowing effect (and--- just like with diamonds--- less brilliance than a round brilliant cut), could you share your thoughts on what you consider to be an acceptable amount of windowing? As I've mentioned before, after doing research on super ideal cut diamonds several years ago I saw a lot of really nice round brilliant diamonds--- stones with a cut quality that put them in probably the top 3% of all diamonds cut annually--- but I have very, very little experience with faceted colored gemstones. When I started getting interested in colored gemstones a little over a year ago I stuck almost exclusively to cabs (which are soooo much easier overall to evaluate than faceted stones--- especially since I only dabbled with inexpensive semi-precious cabs, with a good portion of them being naturally opaque). And while there must be plenty of overspill similarities between a well-cut faceted diamond and a well-cut faceted colored gemstone, in many ways it feels like an entirely different ball game. Like, mind-blowingly so. Beyond the shared cut quality issues that diamonds and colored gems share, I'm already seeing how difficult it is to evaluate colored stones. there are so many factors involved when it comes to just the color saturation/hue thing (with a complicated tightrope situation in terms of stones either being too light or too dark--- apparently finding a happy medium with the color part is abundantly tricky). The windowing thing in particular is something I find myself fascinated by. Up until very recently I don't think I had ever seen a significantly windowed gem (diamond OR colored stone) just because of limiting my diamond hunting experience to super ideal online boutique shops, and sticking with inexpensive semi-precious cabs. So I would love to see some example pictures of what you guys consider to be atrocious faceted oval windowing... medium awful faceted windowing... and acceptable faceted oval windowing. I'm guessing the size of the gemstone would be a pretty large factor, right? I mean, I'm guessing it is generally easier for smaller ovals to pass muster with a little windowing if the overall color saturation is good. The larger the stone, the more unsightly a window would be? Or am I wrong?

Bring on the knowledge, good people--- AND the example pics. And thanks in advance!

 

[gingercurls]

What your acquaintance told you is not correct. Plenty of ovals exist that have been cut correctly that do not exhibit windowing or half and half extinction. In colored gemstones, tilt windows do happen to some degree with all stones.

Here are some threads on PS that discuss windowing:

Window Or Tilted Window

This is not my stone. I post the video because I want to learn about the cut. Is this a window or tilted window? Will you recut the stone in this situation? Why does the dealer prefer to display the colour stone in east west position? Thank you.

www.pricescope.com

window when stone is tilted?

Is it common for a window to appear when a stone is tilted? The tourmaline I just got from Barry does this. I didn''t think too much of it because I figure he is a great cutter and it''s ok. :) However, in the past couple das I''ve read a couple posts that comented on this. The topic was a bit...

www.pricescope.com

 

[lovedogs]

I wonder if the person meant tilt window? Because all ovals I've seen have that to some extent.

 

[gingercurls]

Also, it is important to remember that colored gemstones and how the market for colored gems is very different from that of diamonds. Diamonds are a highly regulated and controlled commodity where is it common for stones to be accompanied by lab reports that provide grades on the quality of the cut. Practices tend to be different for colored gems. Lab reports and the type and amount of information vary more among institutions for colored gems than diamonds. Many colored gems are cut for size and weight and a lot of consumers seem to be willing to sacrifice some beauty and/or optical performance with their colored gems for a stone that is a little larger.

 

[matt_k]

I wonder if the person meant tilt window? Because all ovals I've seen have that to some extent.

I'm assuming maybe he did? But I'll ask!

 

[matt_k]

What your acquaintance told you is not correct. Plenty of ovals exist that have been cut correctly that do not exhibit windowing or half and half extinction. In colored gemstones, tilt windows do happen to some degree with all stones.

Here are some threads on PS that discuss windowing:

Window Or Tilted Window

This is not my stone. I post the video because I want to learn about the cut. Is this a window or tilted window? Will you recut the stone in this situation? Why does the dealer prefer to display the colour stone in east west position? Thank you.

www.pricescope.com

window when stone is tilted?

Is it common for a window to appear when a stone is tilted? The tourmaline I just got from Barry does this. I didn''t think too much of it because I figure he is a great cutter and it''s ok. :) However, in the past couple das I''ve read a couple posts that comented on this. The topic was a bit...

www.pricescope.com

Thanks for the links! I seem to recall someone mentioning the tilt window thing on another thread here, but it went straight over my head. I definitely need to brush up more on this phenomenon, tho, so I'll be checking both of these threads out extensively.

 

[matt_k]

I wonder if the person meant tilt window? Because all ovals I've seen have that to some extent.

This guy is a colored gem dude, so I'm almost positive he meant colored gems. I'm the one who made the--- apparently incorrect--- assumptions about oval diamonds( although I DO think it is considered a settled matter that no other cut can match the brilliance of a round brilliant cut--- diamond OR colored gemstone, providing all things are equal in terms of the skill of the cutter, and the material being cut).

 

[LD]

It's very difficult to make comparisons with diamonds and coloured gemstones. So I would urge you to ignore diamonds for now if you're trying to learn.

There are plenty of precision cut ovals that exhibit no issues and are cut to maximise performance and colour. If you look at the majority of Gene's stones (Precision Gem) they look juicy from all angles.

You don't often see a tilt window in a diamond because of the cut/number of facets. However, coloured stones play with light differently so you may see lighter/darker areas.