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 Post subject: Unheated natural blue sapphire?
PostPosted: Sun Sep 12, 2010 11:49 am 
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Hi all,

A friend of mine brought me a stone to identify. It's very dark blue, almost black in natural light, emerald cut 9.5 by 6.0 mm, 2.11 carats.

Photo's (big ones :) ) are at http://picasaweb.google.co.uk/Keirkof/2 ... directlink
Image

Image

Image
The refractometer quickly learned it is a sapphire, so the identity was not really a problem. What I wanted to ask your opinion about is: could this be a natural, unheated stone? I began suspecting it might be because of a few factors:

- It's very dark. It seems that the color at least does not match the standard 'too good to be true blue' I associate with synthetic stones.

- It has two very crisp looking intersecting feathers on one side. I'm wondering if such sharply defined features would still occur in stones subjected to high heat.

- There are also lots of tiny, regularly shaped dark inclusions throughout the stone. They do not show a pattern of 'dust clouds', nor 'comets' nor 'flux pattern' as are commonly described in synthetics. Though some of the largest inclusions have stress cracks around them, none seem to be 'rounded' or 'exploded'.

- Though there is a lot of colour zoning in the stone, all zones look perfectly straight. I didn't see anything resembling the curved zoning of flame fusion synthetics.

I'm wondering whether this stone could be a natural, unheated one. If it is a synthetic, it looks like a low-temperature one. Could it be a pulled crystal?

I wonder what you guys think. I find one of the most difficult things is to make a guess about the natural or synthetic nature of a stone. It would be a shame to miss the 'one-in-a-million' stone that is actually natural *and* flawless, just on the basis of 'that looks too good to be true - must be a synth' reasoning.

The stone pictured here is not really in that category, mind you. It took huge amount of light before it decided to become transparent :) I'm only wondering what might happen if a fine kashmir or burmese sapphire would materialize on my desk one day... 8-[

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Sun Sep 12, 2010 1:55 pm 
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So hard to tell without being able to see the stone in 3-D and move it around. Someone sure treated it badly, though, didn't they! :shock:

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Mon Sep 13, 2010 7:19 am 
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Indeed they did... Part of the reason why I'm asking is because we wonder if it would be worth having it re-cut...

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Tue Sep 14, 2010 6:42 am 
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Dear!

If you see the third picture of the sapphire you will see the color concentration around a guest crystal. So this is the one of the characteristic of Beryllium heat treated Sapphire or Advanced heat treatment or also called Bulk diffused treatment.

In my personal opinion the sapphire is Natural but Treated.

Hamid Usman Khattak (HUK)

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Tue Sep 14, 2010 12:00 pm 
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Which xl are you referring to?


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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Wed Sep 15, 2010 1:20 pm 
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If you're referring to the largest crystal, visible slightly left of center in the last picture: it is a crystal which looks opaque in this photo, but dark red from other angles. It's surrounded by three features which i would describe as planar stress fractures. The color you see in this picture is due to interference, similar to what you might see in incipient cleavage features in other material. The fractures have no color of their own - from other angles they are completely transparent - to the point of being invisible.

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Wed Sep 15, 2010 4:09 pm 
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I know "to each their own", but do you have a market for such a dark sapphire?? :?

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Wed Sep 15, 2010 4:13 pm 
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enlarge the picture you will see the color concentration (blue color) around a guest crystal.


Attachments:
DSC_0037-1.JPG
DSC_0037-1.JPG [ 28.09 KiB | Viewed 2790 times ]

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Thu Sep 16, 2010 11:58 am 
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Osman khattak wrote:
enlarge the picture you will see the color concentration (blue color) around a guest crystal.


mmm......judging by the suface abrasion i think we're dealing with a very old stone, this particular (but not only this one) made me think it's not berillyum treated......this is my opinion only, of course...
ciao
alberto

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Thu Sep 16, 2010 3:40 pm 
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some features of Beryllium treated corundum


Attachments:
concentration of color.JPG
concentration of color.JPG [ 13.61 KiB | Viewed 2759 times ]

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Thu Sep 16, 2010 3:52 pm 
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beryllium treated corundum features


Attachments:
beryllium treated corundum-1.JPG
beryllium treated corundum-1.JPG [ 19.71 KiB | Viewed 2758 times ]
beryllium-3.JPG
beryllium-3.JPG [ 18.85 KiB | Viewed 2758 times ]
beryllium-2.JPG
beryllium-2.JPG [ 18.1 KiB | Viewed 2758 times ]

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Thu Sep 16, 2010 10:13 pm 
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In blue Be treated stones the inclusions due tend to be a bit different then the rest due to the differing method of treatments needed to achieve it, from what I understand. The blues do typically have a specific type of definitive inclusion, but I can not find the image off hand, sorry. Not on my PC with all my notes and files and reference materials, lol.

I'm not sure there is enough magnification and detail to tell if those inclusions have been subjected to high heat and them getting a halo type effect. I can see what you mean by the blue halo, but I am not sure if it is actually there or if it is a trick of the lens/camera/lighting. They could be blue simply due to chromatic aberrations and such specifically purple/blue fringing or just the Bayer sensor interpolating the data incorrectly. A much more magnified image of them would be necessary to make any conclusive decisions on them IMO.

The crystal that is reddish with the planar fractures, anything like these:
Image
Image

Now, ignore the colors on this last one, they are the same burnt orange/red colors as the others. I forgot to change my white balance settings from a previous source with different light source, lol. But I liked it as is so kept it in a more artistic type value, will eventually correct the color for research reference as well.
Image

If so then your sapphire has most definitely been treated by high heat at least. As these are uranopyrocholore crystals, very indicative of a Pailin region sapphire, and the fractures are caused from the heat. And considering I believe Pailin is the second most common source of sapphires used for Beryllium Treatments it is a possibility. All bearing the above crystals and fractures are what you are seeing inside of yours. If so, I would not rule it out.

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Fri Sep 17, 2010 1:45 pm 
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Hi Osman and thank you for sharing the pictures.

i would assure you i'm aware about the BE treated material features, checked thousands carats of them in last years and i wrote a little article for jeweler posted here : viewtopic.php?f=50&t=8913
Scroll down the thread and click on the image of the magazine's cover (the dog on blue background).
I'm still not presuaded this stone is a BE-trated, at least by viewing those pictures.
ciao
alberto

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 Post subject: Re: Unheated natural blue sapphire?
PostPosted: Sat Sep 18, 2010 3:33 am 
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First of all let me thank everyone for their input on this case. I very much appreciate your help. :)

Swishman, the planar fractures indeed looked a lot like the pictures you posted, especially the second picture where several of the fractures seem to end in a star-like pattern with sharp spikes at the end. The crystals in the stone were a lot darker red and had more well-defined crystal faces, but that will probably not help us a lot further.

Osman, I have looked at the stone very thoroughly and found no inclusions resembling the melted crystals you posted examples of. The color concentration must indeed be an artifact generated by taking the picture, as - besides the interference I talked about - there was no distinct coloring around the inclusions in the stone itself.

I returned the stone to its owner last week as a 'probably natural, possibly untreated sapphire'. Knowing what I know now, I might ask to borrow it a bit longer and pay for a lab examination. There is probably no market for very dark blue sapphires, but untreated natural ones are quite rare nowadays. Just for the interest of a gemmo student. :)

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