Extinction

[T L]

To me, there are three main groups of gem collectors. Some of these groups overlap, but this is what I have perceived at a very high level.

1) Fine color is a must irregardless of cut.

2) Precision cutting is a must, irregardless of the quality of saturation

3) Precision cutting and fine color are a must

Add in a billion other variables to the above (hue, tone, treatment, clarity, gem species, size, etc. . . ), and you get the idea of the complexity of colored gem collecting. The fact of the matter is that collecting colored gems is so complex a subject, that we can discuss cutting all day long, and people will always find no rhyme or reason with the discussions. Colorless diamonds are by far, a much less complex subject, and just a subset of a single gem species.

 

[yssie]

I have to admit I saw this thread, read some of it, and it made my head hurt.

I DO have an appreciation for well cut stones of the colored variety, but my main focus is the color. Cut can help me like a stone where color is lacking, but on the real, if that color is all there, cut? what cut? lol man I will take the stone as long as that color is there 4-real!!(thats not a lie either, I got some stones to back that up! )

Many of us tend to focus on treatments because thats what affects us the most. I'm not saying that cut dosen't because it has bearing, if you're taking about a sapphire thats nuked to hell and back with a great cut and a sapphire that has awesome color but a so so cut, guess which one most people here would buy.

To that end, Gary, I think it all starts with babysteps. Outside of the colors of the stones, Treatments are really the number 1 concern for a lot of us because those treatments can and do affect the colors of the stones sometimes. They certainly can make or break the value of them thats for sure! So I know I don't speak only for myself when I say I would LOVE to see more info treatments and how they're tested for in one space instead of it being spread to the far corners of the internet. If Pricescope had such a resource it would really rock!

And yes as much as I would love for some of my stones to not go dark in certain lights, thats the way it is. I have accepted pretty much as inevitable. The rest of the convo went so far over my head I can't even follow it.

Ok Imma shut up now...lol

-A

That's very interesting.. nothing to contribute to this thread, but in reference to your statement Arcadian - I know which one I would buy, assuming end colour of the nuked sapphire is awesome and treatment is stable and price is decent for the goods - vs untreated naturally awesome colour and so-so cut and very high price.. I'm an RT regular btw, my participation in CS is limited to ogling the pretties

Another thing I notice is that when I see a post asking for suggestions the stone my eyes are drawn to is most often *not* the most valuable or the most desirable colour for that species, but has the facet patterning that I find the most pleasing - whether that happens to be precision cut or "native cut". I also apparently usually prefer stones that err orange or brown or grey over more - saturated, I guess? - colours, and I generally like paler gems more than vividly coloured ones.

I guess I'd be TL's type 2.

ETA: I confess I am finding the disdain for diamonds that is clear in this thread to be quite amusing. I would submit that material for D IF stones is neither cheap nor easy to find, yet just a couple of days ago we had a poster on RT looking for exactly that - and who wasn't willing to compromise on cut quality (as The Diamond People define it, anyway ).

 

[LD]

Cut is not what coloured gemstones are about - hence the total lack of interest from this side of the forum. Generally speaking the normal consumers on this side of the fence are not the least bit interested in light performance or math!

Well that depends LD. Many of the consumers on this forum are not in a position to purchase stones in which the color is SO GOOD that the cut doesn't matter. With some of the fluorescent spinels and rubies which have been posted here recently, as well as the electric colors of some blue and green tourmalines, the cut of the stone really has little to do with how the color is presented in the stone, this is because the material itself does actually glow and has light distributed from all parts of the stone by fluorescence and micro inclusions.

With much lower valued stones that do not have such grand internal properties, the cut is what brings the color out in the stone and makes it what it is. In that regard the cut is everything, since without it you can end up with a "black hole". The really odd thing to me is why people here are so focused on only the very best materials and NOT on good cutting which can make modest materials look much better. It seems to be either "all or nothing here" instead of a more thoughtful and perceptive position of people becoming more astute in their perceptions of some gems which are attractive in their price points and with certain reservations about where they can be worn effectively. Cutting to minimize extinction is critical in many stones where excess extinction is visual death to that stone. Recognizing when you're actually looking at extinction or are just in the wrong lighting environment, is also critical when buying lower valued stones which may be acceptable to their owners in a different environment.

Michael you've been around this part of the forum long enough to know that I have a reasonably extensive collection and I'm not arguing that in a lower value stone cut can play a part in making an otherwise dull stone, prettier, but I'm looking at this argument from my own personal standpoint which is a collector of many years (starting at an early age I hasten to add ). I have a considerably large collection of Alexandrite and Paraiba (or Cuprian if you prefer) Tourmaline. Now, bearing that in mind, ........ if I was going to be fussy about a cut on an Alexandrite, would I ever buy a stone? Very rarely! As it happens most of mine are cut well enough to be adored and loved AND hold considerable value. I'm yet to see a precision cut Alexandrite. Alexandrite is nearly always cut to preserve weight because the material is so sought after. If you find a well cut one it's an absolute bonus.

Now, turning to Paraiba Tourmaline, most of mine were bought about 10 years ago. At the time there was a fair amount of material on the market at reasonably affordable prices. How many precision cut pieces did I see? Not many. How many PT's do I own that have been cut for performance rather than weight? None. Again it's "normally" about preserving weight and colour. A brilliant example of this is my 6.5ct PT that had a reasonably large window but phenomenal colour. I really wanted it re-cut to reduce the window. Had I done so, I'd have lost more than half the original weight, there were no guarantees the colour would be better and the value of the stone would have plumeted! In the end, I set it in a ring and, yes, you've guessed it, the window is less apparent! Do I regret not having it recut? Absolutely not.

If I were offered (for example), a 3ct great colour changing Alexandrite, eye clean with a precision cut and exactly the same with a poor cut which would I choose? Of course it would be the better cut stone BUT everything else would have to be equal. Taking another analogy, if I were to be offered a 3ct great cut Alex with a weak colour change and a 3ct poorly cut Alex with a phenomenal colour change, the latter would be in my collection without a hesitation - cut wouldn't be a consideration.

So I DO understand why people would like cut and colour to be equally important AND I do understand that precision cutting can enhance the beauty of a stone BUT I've also seen it where it's actually reduced the colour impact and where it's far less important. So am I convinced by anything I've read in this thread so far? No. It's not because I don't want to learn. I do. The fact is that if all coloured stoners worried about angles etc., they'd never buy anything. It's far more fun having the world as our oyster and not having that particular worry! Cut is a nice to have bonus NOT a prerequisite for many. I don't need graphs, maps, diagrams to help me judge a stone. I know when a cut is "off" and I know how it affects performance. Many on this forum do. I can see the discussion of this thread applies to diamonds and fits in very well there but my personal opinion is (and I would think it's shared by the majority of regular contributors on this forum judging by the tumbleweed that blew through it for a few pages) it doesn't fit comfortably in coloured gemstone world.

 

[gsellis]

I have been not pointing this out, just to avoid confusing the issue, but I figure I might as well get it off of my chest.

The white card with a hole cut out, hiding the camera... That is a diffused light source. While it might hide some shadowing, it will still have a lens shadow (move it back to minimize it). Also, because it is diffuse over a span, it will also minimize any true extinction as it now gives 360 lighting on the stone.

BUT, if you use the same idea, a white piece of paper with a hole in it, if you think you have extinction, that will quickly rule out a shadow. It will hide your shadow. It might get some strange looks too. But some folks are into that. So ask a Goth to do it for you.

 

[T L]

This is a very interesting topic, but again, to my earlier point, colored gems are so complex. I think we'd get a much more constructive conversation if we discussed something more specific like, for example, "the precision cutting of medium dark to dark blue spinels to get optimal color and sparkle and less extinction (blue spinels in darker tones are prone to extinction)." Each gem species is so very different, and then you're factoring different hues, tones, saturations, RI's, etc. . . that it is so difficult to cover this subject in just a single thread. I do think it's interesting though.

 

[Arcadian]

Hi Yssie I don't think its much distain as it is in many ways...confusion. And there's a lots of people here who really do love diamonds as well as colored gems. Me personally, I don't really like D colored rocks (guilty as charged!) as a center stone, M colors and below? yah those really rock! but I'm pretty bad though

I think its really a matter of what we want and are used to. for some its easy to straddle the line so to speak. I wish I could but well, I'd be broke...lol


-A

 

[yssie]

Hi Yssie I don't think its much distain as it is in many ways...confusion. And there's a lots of people here who really do love diamonds as well as colored gems. Me personally, I don't really like D colored rocks (guilty as charged!) as a center stone, M colors and below? yah those really rock! but I'm pretty bad though

I think its really a matter of what we want and are used to. for some its easy to straddle the line so to speak. I wish I could but well, I'd be broke...lol


-A

Oh my edit wasn't to anything you wrote Arcadian. I can honestly say I find uniqueness in every diamond and every coloured stone I see, so to hear from people who feel otherwise is an interesting - well, to me, admittedly baffling - perspective. But then, to each his/her own.. and sadly I'm not going to be doing much straddling either, for that same reason

 

[Garry H (Cut Nut)]

I have been not pointing this out, just to avoid confusing the issue, but I figure I might as well get it off of my chest.

The white card with a hole cut out, hiding the camera... That is a diffused light source. While it might hide some shadowing, it will still have a lens shadow (move it back to minimize it). Also, because it is diffuse over a span, it will also minimize any true extinction as it now gives 360 lighting on the stone.

BUT, if you use the same idea, a white piece of paper with a hole in it, if you think you have extinction, that will quickly rule out a shadow. It will hide your shadow. It might get some strange looks too. But some folks are into that. So ask a Goth to do it for you.

Hi George,

I could have taken the photo through a much smaller pin hole - but i felt the result was enough to show the issue?
(btw the Goth would need a goth white camera lens to hahahaha)

 

[Garry H (Cut Nut)]

This is a very interesting topic, but again, to my earlier point, colored gems are so complex. I think we'd get a much more constructive conversation if we discussed something more specific like, for example, "the precision cutting of medium dark to dark blue spinels to get optimal color and sparkle and less extinction (blue spinels in darker tones are prone to extinction)." Each gem species is so very different, and then you're factoring different hues, tones, saturations, RI's, etc. . . that it is so difficult to cover this subject in just a single thread. I do think it's interesting though.

This is a dark blue sapphire example TL, not spinel. But it shows how size matters with material color.
There are several other examples on that same page that I linksed to above
http://www.octonus.com/oct/projects/modeling.phtml

There is plenty of material that gem lovers can read there.
If anyone wants to point to any of the stone files and asks me to do an experiment in DiamCalc I am happy to do it.

 

[Arkteia]

Sorry I could not follow the whole discussion, and my question might have already been answered somewhere, but in case it was not, I would like to ask it.

I never saw Glenn Lehrer's designs in real life, but is there any extinction seen in his cuts of flat rough?

 

[beryl]

. I repeat this excerpt from the preface to my reproduction of 'Faceting Limits' in 1987.
"... there has been a tendency to over-rate the value of this work.
"We now cut stones only for profit and focus on those factors which most affect salability:
...... GOOD MATERIAL - color and clarity count most,
...... GOOD POLISH ---- important to brilliance,*
...... FLAT FACETS ----- inportant to scintillation.
"We use mostly traditional cuts and facet slopes,**

* Today I would use the term 'brightness' instead of 'brilliance' - because 'brilliance' requires contrast as well as 'brightness'.
** At that time I did not realize that the 'traditional facet slopes' that had evolved were those which gave maximum 'brilliance'. Garry was first to point that out in 2000. We made traditional cuts because there were ready-made settings available and we could put them into whatever setting the customer chose; that is important for the retailer, few customers want the cost of special settings.

 

[beryl]

. So who among you are going to Tucson this year? May be a bit dicey because of the shooting.
. 3 years ago in Brazil, a miner told me he was buying stones at Tucson to sell to the Gringos when they come; the mining in Brazil is severely reduced because of new laws similar to our EPA. 20 years ago it was gem buyer's paradise - 1/10 US retail at the mines..

 

[theredspinel]

Wow. I know this is a major old thread but wow so interesting! Not just the discussion (that I for one am glad was had here; it might not be specific to CS but it definetly opened my eyes to a world I never would have ventured into otherwise) but seeing how opinions have changed over the years.

I know colour is still king but boy will you hear it here if you aren't looking at a well cut stone which is great because all education is great. I'd rather know and make an informed decision to buy a badly cut stone (which I'd have my reasons for) then not be aware that it's not a superb cut.

I like saying "education can't be a bad thing".