Another Window Question

[minousbijoux]

Okay, experts, please weigh in. This looks like it has a window to me, both in the video and in the still shot. However, the depth, if their dimensions are correct, is .80. So if its windowed, is this a case of perhaps U cutting on the pavilion affecting light reflection?

http://cgi.ebay.com/1-82ct-Top-Notch-Scarce-Oval-Greenish-Blue-Tourmaline-/350275568448?pt=Loose_Gemstones_1&hash=item518e0d0340#ht_2454wt_917

 

[LD]

Yes windowed. It's very apparent in the video and still shots. However, it's a gorgeous colour and a lovely gemstone. It will probably not be as obvious when set BUT it may also darken. I was looking at this one a while ago and spent ages pondering. Ultimately I didn't pull the trigger because I thought it might lose the gorgeous two tone(ish) look when set and be too dark especially if I set it with a more closed basket to minimise the window - it was a bit of catch 22 situation. If you do get it, I'd love to see photos!

 

[chrono]

Definitely windowed in both the picture and video. The total depth is deep because part of it is in the very high crown, and probably the angles on the last few tiers on the pavilion isn't ideal for the stone. I'm with LD on what to do about setting it; if in an enclosed setting, the stone might darken up too much but in an open setting, I don't know how obvious the window will be.

 

[minousbijoux]

LD and Chrono:

Thanks for your responses. I'm still back trying to figure out why its windowed. Since it has the depth, I'm thinking that the fact that the pavilion rounds in toward the culet must throw off how it reflects back - or perhaps there is too much height on the crown and not enough on the pavilion?

 

[LD]

Minous - don't bother trying to use numbers (i.e. depth) to work out why something has or hasn't a window. In diamonds, numbers are useful but in coloured gems, eyes are the best evaluators! Native cut gemstones can be windowed because of facet placements and I'm pretty sure that's the case with this gem.

 

[chrono]

In this case, the reason for the window is the last few critical angles in the pavilion. Depth alone doesn’t necessarily tell you if it is windowed or not. When a stone is overly shallow, yes, but when it is deep or even very deep, a stone can be windowed if the angles are not correct. In this case, the angles are not cut correctly to return light back to the eye, thus allowing some leakage. There is also no way to guess at this by just looking at how the culet area is cut. Every gemstone has their own critical angles depending on the RI, and other host of factors. The only way for a consumer to tell is by looking at the view straight down the table into the stone.