More Teaching Requested Please

[JewelFreak]

Recently I've been doing my homework on colored stones -- I hope you folks can tell me if I've learned anything at all. Especially without seeing a stone IRL, it's hard to evaluate. So my questions have to do with cut, clarity & photography.

As an example, here is an Odyssey untreated Tsavorite 1.64 ct., 7.5 x 6.2 x 4.2. (Vendor's pic and a screen capture from his video.) This is the site if you care to check out the vid: http://cgi.ebay.com/1-64ct-Unbeliev...595?pt=LH_DefaultDomain_0&hash=item35a91ffd13

The scintillation in the crown looks very good to me, but is that a big window you see in the table or reflection from lighting? The table is large, am I right? I work out the depth ratio as 61% -- is this shallow enough to cause a window? If the crown were a little deeper, maybe resulting in a smaller table, would that work better?

Re photographing stones, to compare -- the 2 sapphires come from past Sotheby's catalogs. Both untreated, sold for megabucks. The tables on both look comparatively smaller than on the Tsav but still there's a dull area in their centers. These sapphires are in settings, which could make a difference in how they photograph. So, in a picture, how do you distinguish reflection from problem?

Any other comments are welcome! And thanks!

--- Laurie

 

[davi_el_mejor]

I'm pretty new to collecting and learning along with you, but I'll give you what I see and hopefully the more educated posters can agree or give their differing opinion.

The stone seems a little overpriced to me(just my opnion).
Very clean. The color is a nice green, very little modifiers, if it isn't a true green, I would say it would be more yellow green than blue green. I think the pictures show a tilt window. It looks to have a very small window in the very center, but definitely not as dramatic as what we see in the video. Saturation is something I'm working on understanding on how to describe, but I would say the saturation is good. It looks like it can go extinct easily though, but that's hard to tell based on the video and picture. I don't think the table is large and I don't how a smaller table would effect the appearance of the stone.

The sapphires:

I think it's just the photos. The first sapphire looks more grey and less saturated than the second. That's all I have on those, I don't know how settings effect the appearance. Most of mine are not set.

 

[serenitydiamonds]

To be quite honest, photos are not accurate enough for color gemstones to make the decisions or assertions you are looking for. You must inspect the gem in real life. It's very difficult to discern the true color of a gem based on it's photo, the extra yellow could be from lighting, shadows, camera sensor color bias, your monitor's color calibration, or a million other sources. Digital cameras also have poor response to the color green, so images are typically adjusted to make them similar to real life. The picture also appears to have had it's color contrast increased a lot, which also affects how it looks.

I see reflections of the pavilion facets, but I'm not sure if it's a window or not. You could ask the vendor to place the gem over a piece of paper with text on it and take a photo. With color gems, return and inspection policy is the most important.

--Joshua

 

[Agnesg]

another rich green..its a shame on the shallow cutting.

 

[JewelFreak]

Thanks everybody for your input. I wasn't seriously considering buying this tsav -- but it's a good example of what confuses me when looking at stones online -- it's darned hard to tell what I'm seeing. Another part of that -- it comes through on my monitor with more blue than yellow. Didn't realize about cameras not being sensitive to green, Joshua, interesting factoid. There's enough extinction in it that I suppose the cutter thought he couldn't make it any deeper cut. Anyway, your thoughts on reflection or window are helpful. The bottom line, of course, is that it has to be seen in person.

--- Laurie

 

[chrono]

I’m not seeing a big window at all, it looks like there is a very small window and what you could be seeing is a tilt window which happens when the stone is viewed at an angle. A window is caused/created when the angles on the last few tiers in the pavilion is not cut correctly; sometimes there isn’t enough depth to do so and sometimes, it is deep enough but the angle isn’t correct. The effect of a higher crown coupled with a smaller table helps the stone sparkle (show brilliance and fire) better than a flat topped stone. However, it would require the total depth to be deeper as well to account for the pavilion angles to be cut to also reflect light back to the eye correctly. I don’t consider the stone to have such a large table and see it as quite normal sized. Personally, I’d first go for colour I prefer first, with some give and take for the cutting.