spinel question

[pad3006]

Hi everyone;
I was wondering if cut makes a big difference in gem stones such as Spinels?
I got one that I bought appraised and the report said that the cut was "good", I know that with diamonds an ideally cut diamond sparkles a lot more then a regularly cut one. Is it the same with spinels? thanks

Phil

 

[Matata]

Strmdr has a good bit of info about cut here.

 

[valeria101]

Not everyone uses the ''ideal cut'' lingo - actually, Ive neaver heard this about colored stones. If they have a set of cut quality steps than it is defines in house and the only one knowing if there is any better than this ''good'' and why is the person who gave the label.

The optics of any cut on any material can be analyzed and ''optimized'' just like it is done for ideal cut diamonds. For colored stones, this is harder because it involves color as well as brilliance to begin with. The only reliable way to find out if a particular colored stone will benefit from recuting is... to ask a cuter - there are just too many details involved to talk about what is good or bad on average, as it is done for diamond cut standards like the HCA.

Just my 0.2 worth opinion, of course.

 

[glitterata]

You''re probably asking something much more precise than this, but a well cut spinel will look much better than a badly cut one. I don''t know how much better a really, really, REALLY well cut one will look than one that''s just decently cut, though.

 

[rubydick]

Like all gems, cut is an important aspect. But unlike diamond, the cut of colored stones is not simply about capturing light and returning fire and brilliance. The cut of a colored stone is primarily about grabbing light and returning it as color, but not just any color, but something as intense and saturate as possible.

This requires a completely different approach than that of diamond. Diamond has the ability to return much light, but because of its high refractive index, it also loses a lot at the external surfaces (something we call luster). Metals have the highest luster, but also have little color, since virtually no light enters them. This partially helps to explain why the colors of colored diamonds are generally so insipid.

So when looking at a colored stone, throw out the diamond grading book. It doesn't apply. Some of the richest colored gems (emerald being a prime example) have low refractive indices.

Bottom line: cut is important, but let your eye be the judge of what works. Don't get hung up with angles and refractive indices and other forehead-angle measurements of intelligence. Let your eyes walk you to the best looking lass on the catwalk.

 

[valeria101]

Pad3006, You can probably tell where I learned my cut mantra from:

Date: 9/15/2005 12:26:06 AM
Author: Richard Hughes

The cut of a colored stone is primarily about grabbing light and returning it as color, but not just any color, but something as intense and saturate as possible.

Actually, this has been said before on this forum here: it is either brilliance or color... etc. It just so happens that either great brilliance or great color make gemstones darn valuable. But there is allot in-between and not much is said about those. Kind' of pity, in my opinion.

Thinking of light colored pink spinel, or things like morganite and your usual green beryl and aquamarine or kunzite or pale sapphire or those mint colored garnets mentioned on another thread nearby... those are nice too, although they do not come with either top brilliance or top color. For them, cut can do allot and given the (relatively) moderate cost of the materials this can be expected. There is allot written online about fancy gem cutting (try faceters.com for a taste).

Depending on what spinel you have in mind (dark or light, saturated or not, expensive or not ultimately) - cut means different things.

Hope some of this makes sense

 

[Sagebrush]

Cut is a very important factor in colored gemstones. A well cut stone may not be fine but a fine stone is always well cut. As Dick points out the issue in colored gems is the delivery of colored brilliance as opposed to brillance without color in the case of a diamond.

In diamond, cut is the first and most important of the 4 Cs in both the quality and value equations. Diamonds are cut to a standard that enables the return of 90-98% of the light that enters through the crown back to the eye in the form of brilliance. This is quite a feat of engineering! Colored stones never approach this standard. 80-90% is considered optimum. Why, because the job of delivering colored light is more complex and in colored stones Color; hue/saturation/tone is the 1st C.

In the connoisseuship of colored gemstones there are four factors, color, cut, clarity and crystal. These are the four C''s of connoisseursip. There importance and relative weight in the value equation may vary but in a fine gem all are present.

 

[pad3006]

Hi everyone;
Thanks very much for the responses.
The spinel that i have is very saturated in color it is a very nice pink color and the stone is very bright. I guess that is a good thing judging from what I read about how color is so important in gemstones.
The report I had done on it said the color was "slightly brownish, slightly purpleish red color" I was not exactly sure what that means but it looks very pink to me but I guess I have an untrained eye.
Thanks for your help guys.

Phil

 

[valeria101]

Date: 9/15/2005 8:50:19 AM
Author: pad3006

...it said the color was 'slightly brownish, slightly purpleish red color' ...

'Guess that is playing with words... Not sure what is the use of the system, but for some reason this is how competent guys talk about gem color. The lab should have a definition backing these names because there isn't a standard one.

 

[Cave Keeper]

So, should colored diamonds be considered from the viewpoint of diamonds (i.e., cut is of prime importance) or from the viewpoint of colored stones (color is of prime importance)?

If the latter, then maybe colored diamonds should not be cut in the form and exact proportions of standard Brilliants, like colorless ones? I wonder if those concave cuts which can make an Imperial Topaz look like a golden stone will work for a colored diamond, especially in turning a Fancy Intense Canary yellow one into a Fancy Vivid Canary yellow (or, better yet, gold-like) one.

 

[valeria101]

Date: 9/15/2005 10:10:27 PM
Author: Cave Keeper

If the latter, then maybe colored diamonds should not be cut in the form and exact proportions of standard Brilliants

But indeed they are not. Even if you do find a round shape, chances are it would not be AGS0 (insert shrug here). The only company which cuts vivid fancies H&A is... Takara, and don't ask me why even they insist on doing this.

I wonder if those concave cuts which can make an Imperial Topaz look like a golden stone will work for a colored diamond,

Concave cutting cannot be done on diamonds - the tools are not out there yet, I've been told. I don't think CZ was done either. The closer you will find is natural white zircon.

For some reason, I didn't think of concave cutting as a color enhancing trick. Is it ? Is the respective topaz online ?


This is all that comes to mind.

As far as I know, the 'optical design'Garry talks about has to follow very different goals if color is to be improved. Not that these issues got allot of coverage for H&A on the forum, but color needs a totally different starting point anyway

 

[Sagebrush]

Date: 9/15/2005 10:10:27 PM
Author: Cave Keeper
So, should colored diamonds be considered from the viewpoint of diamonds (i.e., cut is of prime importance) or from the viewpoint of colored stones (color is of prime importance)?

Color is the first (C)onsideraton in the valuing of colored diamonds. I was offered a pair of red diamonds that resembled really poor rhodolite garnet (0.82tw). In fact, had they been rhodolite garnets no one would have given them a second look or paid any more than 5 bucks for both. What you might call aquarium gravel quality. Still they were $250,000 for the pair because the tiny bit of feeble brilliance they could muster, showed red and they had a GIA cert attesting to their red-hood.

It is quite instuctive to look at the relative weights placed on Color/Cut/Clarity in colored diamonds. Clarity, or at least loupe clarity, is least important. There is eye-clean and very little attention paid to any clarity grade above SI1.

The rarer the color (colored diamonds) the less consideration is given the other two Cs. This sharply underlines my contention that the loupe grading standard is a phony standard that was introduced to make what was not rare seem rare. If the standard is beauty, why pay the premium for anything above eye clean (SI1)if, by definition, what ever is in the gem "does not materially effect either the beauty of durability" of the gem?

 

[colormyworld]

I am no expert but I think "slightly brownish" is a gia term for saturation. How about a picture?

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" src="http://www.pricescope.com/idealbb/images/smilies/36.gif" align="absMiddle border=0">

 

[pad3006]

I tried to post the picture of the picture of it but it wont let me which is strange b/c I have posted it on here before. I dont know how to post a link but if you look under my name you will find it.

 

[valeria101]

Date: 9/19/2005 12:31:06 AM
Author: pad3006
I tried to post the picture of the picture of it but it wont let me ...

This one ?

Sure remember that! and I see why you are asking about cut. I love it as is just like all old or 'native' cuts - I like being reminded that the precious wonder infront of me is actually stone from the ground, not candy. In particular, this stone reminds me of a certain type of old mine cut that is considered the precursor of the modern 'emerald cut' in diamonds - quite delightful. : )

But from a cold, technical & impersonal perspective, between this and geometrical perfection (whatever that is good for) there is a bit of room. The intervention does not have to be severe either: Take a look...

Assuming the stone is not yet set, what are your plans?

 

[colormyworld]

Val that link was very interesting. I don't think I would recut that spinel unless it is windowed badly. I like stones with a little personality as opposed to one that looks like it came off an assembly line! That is a very beautiful spinel by the way.

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" src="http://www.pricescope.com/idealbb/images/smilies/36.gif" align="absMiddle border=0">

 

[pad3006]

Thanks Val, yeah thats the stone. I think it really looks so nice the way it is too.
I think your right that it looks nicer the way it is then to have it recut to look faceted like a diamond is. thanks again

Phil