Another Ceylon Blue Spinel (or three)

[colorluvr]

Please bare with the long post, but when ever someone mentions blue spinels and especially cobalt blue spinels on this forum the questions abound, so I thought I'd try to answer some of them in advance.

I'm sending the largest of these three blue spinels (6.12ct) off for a recut because it's a deep, poorly cut stone. It also has an inclusion that can be easily seen when magnified, but not with the naked eye. (which was honestly advertised that way by the seller), but I think it has great potential and it's big enough to afford to lose some size. I took some pictures of it yesterday, but because of the crappy cut, the pictures don't do the color justice, but a few of them capture what I see as it's "potential". This stone WAS advertised as containing cobalt, and I specifically asked the seller whether this was a cobalt colored spinel or a spinel containing cobalt and this is what he said:

"...these are a very rare types of Spinel resembling blue sapphire and they are colored by cobalt. Those are found only in Sri Lanka in any appreciable quantities....."

To answer all of the inevitable questions: No, it does not currently have a cert, but I plan to get one after I get it recut. The seller has an excellent reputation and I do have confidence in them, but yes, I am going to confirm whether or not it contains cobalt if the recut turns out well. I did not initially spend enough on the stone to warrant requesting a cert because even if the stone does not contain cobalt, I only paid a "blue ceylon spinel" price for it, not a "cobalt containing blue spinel" price and the fact that the type of inclusion that it has helps me to feel confident that it's not synthetic.

The seller is Ravenstein-investment-gems and they have very good feedback and have been around for a long time. Every gemstone I have ever purchased from them has looked better than their photos or videos, so "glamour shot photos" aren't a worry. Their ebay auction ads can be a bit irritating as they advertise almost ever stone they sell as "one the most rare on earth", but to give them their due, they often do deal in some of the less "run of the mill stones".

This is what their auctions say about their stones: "At RAVENSTEIN GERMANY we precisely hand cut all gems in our European Union cutting facilities from mine-direct sources of top quality, hand-selected rough. Our prices are strictly factory-direct. Our highly skilled master cutters facet all gems under strict German school “Idar Oberstein” and Bohemian school “Turnov” quality standards."

HOWEVER, this stone was NOT cut by them, but is rather a "hand cut stone" that they sourced from Sri Lanka that was cut in that country and as stated above, the cut was very honestly advertised as only "acceptable". It's the only spinel I have ever seen on their site and the only one their stones that I have seen advertised as native cut.

It was on their site for a long time and I finally caved and made them an offer.

I've had several back on forth emails from Ales, on this stone and others and I believe he is the owner, but I don't know that for sure. He divides his time between Germany and Tuscon.

The two other blue spinels in the comparison photos are certed spinels, but neither claimed to contain cobalt. The round is a gorgeous color and after a couple of surface nicks are fixed, I plan to have it set as an eRing. The bluish gray cushion has a very nice cut, but definitely is more grayish than the others.

First a few photos of the largest cushion:

 

[davi_el_mejor]

Colorluvr, I can see the potential too! I agree it could use a facelift and hopefully it doesn't loose too much weight. I'll keep my fingers crossed for ya.

 

[colorluvr]

Some comparison shots that do a better job of showing the color of the larger cushion. The ones on my hand are not well focused but do the best job of showing off the colors.

 

[colorluvr]

Shots of round spinel and grayish blue spinel

 

[colorluvr]

Colorluvr, I can see the potential too! I agree it could use a facelift and hopefully it doesn't loose too much weight. I'll keep my fingers crossed for ya.

Thanks, it will either be a really pretty stone or a fairly expensive failed experiment

 

[chrono]

I have two true cobalt blue spinels (certed by AGL as coloured by cobalt) that also exhibit a sapphire blue like blue. As I was shopping around for the past few years for a true cobalt blue spinel (cobalt coloured and cobalt bearing), I noticed that there are many differences between the two.
1. Not all cobalt bearing spinels are created equally; some are very dark, some are very gray, but only a few are knee weakening gorgeous.
2. Many vendors use the term cobalt spinel loosely. Most are inferring that the blue colour is reminiscent of the colour cobalt, not that it is cobalt bearing.

I have also come across a handful of gorgeous blue spinels that are not coloured by cobalt. These saliva inducing gems have come mainly from Luc Yen, Vietnam and also Tanzania (but to a lesser degree).

Colorluvr,
I see the potential but I’m not sure how much improvement you’ll see because of the dark tone of the body colour. I hope that at least a recut will give it more blue flash.

 

[LD]

Colorluvr there are a number of very very pretty blue spinels owned by forum members - I'm not sure if the photos are still there after PS changed but it's worth having a look. There was a plethora of threads about blue spinels a year or so ago and some eye wateringly beautiful stones to oogle at!

Good luck with the recut but may I urge caution? If the spinel is indeed coloured by cobalt then I wonder if you would decrease the value by cutting the carat weight in half? It might be worth sending to a lab first and then making a decision on a recut after? Just a thought!

 

[colorluvr]

Colorluvr,
I see the potential but I’m not sure how much improvement you’ll see because of the dark tone of the body colour. I hope that at least a recut will give it more blue flash.

That's what I'm hoping for also. It is a nice color in some lighting (as seen on my hand shots) so I'm hopeful for some improvement. The round spinel is a really really pretty color of blue and was purchased for the color, not for whether or not it contains cobalt. The grayish blue was my first blue spinel purchase and while it is a nice looking stone, it definitely has some gray to it, but the vendor photo showed the true color, so I have no complaints on that end. It's a very "steely blue" looking stone IRL.

The round and the grayish blue cushion are both very clean gems and were rated as VVS, so I'm glad they came with certs.

Chrono - question for you. Does it require the AGL prestige report to find out if the stone contains cobalt or will the brief tell me that? TIA

 

[chrono]

The AGL brief is sufficient.

 

[colorluvr]

Good luck with the recut but may I urge caution? If the spinel is indeed coloured by cobalt then I wonder if you would decrease the value by cutting the carat weight in half? It might be worth sending to a lab first and then making a decision on a recut after? Just a thought!

Question to LD (and other long time collectors) about the above comments. Let's assume that the stone proves to contain cobalt by AGL..... how much does that increase it's value? I don't purchase my stones with the idea in mind of reselling them, however, it is nice to know that you have a reasonably valueable stone that you didn't pay an arm and a leg for. I purchased the stone knowing that the cut was poor with the intention of having it recut. What do I gain by leaving it as is (assuming it contains cobalt) other than just knowing it has value?

I quess what I'm asking is when do you keep a stone as is and when do you recut it to make it more attractive, even it is decreases it's value. I had initially planned on setting this stone in a ring, however, that would probably be a long ways down the road as I have several now that I would probably set before that one...

I appreciate all comments - thanks.

 

[T L]

The AGL brief is sufficient.

I think that can be determined with a chelsea filter as well, although synthetic spinels also glow red under the chelsea.

 

[colorluvr]

The AGL brief is sufficient.

ok, thanks (I responded to LDs comment before I read this answer).

If an AGL brief is sufficient to verify if it contains cobalt, then I might very well do that before I decide if I am going to have it recut.

 

[colorluvr]

The AGL brief is sufficient.

I think that can be determined with a chelsea filter as well, although synthetic spinels also glow red under the chelsea.

Thanks! I bought one of those bright red glowing spinels waaaaay back - live and learn, thank goodness it was cheap.

 

[PrecisionGem]

Where your hopes on the recut to remove the inclusion? From the pictures, that inclusion looks to be right about the depth of the girdle and moving in horizontally to the table. It would greatly reduce the size of the stone to cut away inclusion. A complete recut (crown and pavilion) but leaving in the inclusion could help to brighten up the stone, but the inclusion would still be there, only now closer to the table, and most likely more visible.

 

[chrono]

A Chelsea filter can be used for a quick but not conclusive test because the natural cobalt spinel will appear red (or orange/red depending on cobalt content) colour similar to that of the synthetic cobalt doped stone. The lab will probably also run a few other tests for definitive results:
1. Spectroscope: the spectrum will show the cobalt spectrum of 3 broad bands in the orange/yellow/green. In addition, there is the natural blue spinel spectrum (diagnostic) with lines in the blue area which are not normally seen in synthetic spinel.
2. UV: The natural spinel will be inert under LW and SW, while the synthetic will show chalky bluish-white under SW.
3. Refractometer: Cobalt spinel may have an R.I. of around 1.718 rather than the normal Sri Lankan spinel R.I. of 1.712 still well below that of the 1.728 of synthetic spinel.

 

[LD]

Colorluvr - you asked when people decide to recut and not? I gave an example yesterday in another thread where I had a 6.5ct Paraiba tourmaline with a window. Recutting would have reduced the stone to half (if not a quarter) of the weight. The loss in carat size would have had a huge impact on the value of the stone. The colour is magnificent (to me!) and there is always a risk that a colour will change after a recut - sometimes not for the best! When I found out how much weight I would lose with a recut (it was a very shallow stone to start with), it made no sense to recut. It's now been set and the window has minimised - boy am I glad I set it and didn't recut!

 

[maebelle]

I love the round!

Can we have a picture of the largest cushion pavilion side up? you can sort of see the belly in one of the shots, but I clearer picture might be nice

 

[colorluvr]

Where your hopes on the recut to remove the inclusion? From the pictures, that inclusion looks to be right about the depth of the girdle and moving in horizontally to the table. It would greatly reduce the size of the stone to cut away inclusion. A complete recut (crown and pavilion) but leaving in the inclusion could help to brighten up the stone, but the inclusion would still be there, only now closer to the table, and most likely more visible.

Gene, thank you for your input. I know a recut won't remove the inclusion - there would be no stone left! I magnified the stone and put intense light on it to show the inclusion (and I've added a few more shots I just took). But I truly cannot see it without magnification and a direct light on it. It just starts showing up when I put the stone under a 5x magnifying lamp that has a circular flourescent light that shines down on whatever you are magnifying. Under the 5x, when looking at the stone from the top, the inclusion almost looks like it is part of the faceting (sorry I am so bad at explaining this). The camera flattens out the stone, so it looks much more obvious than in real life 3D and it also makes the inclusion look lighter than it does IRL.

I don't know the technical term for the inclusion, but it is very flat when you look at it from the side, and looking at it from the top of the stone you are seeing the inclusion at an angle if that makes sense. It is not nearly as visable as the photos make it seem, but I do understand what you mean by stating that it will be closer to the table and possibly more visible. The inclusion looks to me to be the same color tone as the stone, only just lighter, but I'm not an expert, so I will defer to you on that.

Here are some more inclusion shots I just took:

 

[colorluvr]

I love the round!

Can we have a picture of the largest cushion pavilion side up? you can sort of see the belly in one of the shots, but I clearer picture might be nice

Belly shot that I took yesterday - slightly lightened to show faceting better. The stone's measurements are 10.5 x 9.5 x 7.1 mm

I think one of the inclusion shots I just did also shows it from the side. I didn't take one (yet) of pavilion side up. You can see the inclusion in this shot also just left and down a bit from the nick that is on the girdle.

 

[LD]

In two posts above, the last picture - side on of the cushion showing the inclusion - is excellent.

When you look through the loupe what does the inclusion look like? Does it look like a feather or a fingerprint or something completely different?

 

[colorluvr]

In two posts above, the last picture - side on of the cushion showing the inclusion - is excellent.

When you look through the loupe what does the inclusion look like? Does it look like a feather or a fingerprint or something completely different?

I couldn't really tell under the loupe, so I looked at it under the microscope and I would say between the two, it's probably a fingerprint. When you magnify it that much you see that it's not solid, and so looks more like the fingerprint.

 

[Aoife]

Wow, these photos are excellent, I totally impressed at how clearly the inclusion shows up.

I can see why you are thinking about a recut, and I'll be interested to hear more discussion from the experts about that. I hope whatever you decide to do you'll post about it here.

 

[colorluvr]

Update:

Decided to do the chelsea filter test to check out the biggest cushion stone....At first I wasn't seeing much of anything, but I have a time with a chelsea filter because I have to put it between my eye and my reading glasses to see anything and then I remembered I still had that big 'ole synthetic blue spinel that shines under a chelsea, so I dug it out and positioned it so I could see the red and then held the big cushion next to it under the same lighting to compare. I was pretty sure I could see red, but the light just wasn't bright enough to shine through the stone much so I wasn't sure.

I did some reading online about using a chelsea filter and one of the gemology chat forums said that the best light for using a chelsea filter was tungsten lighting. My DH has an old Olympus tungsten light with a voltage meter (from years and years ago when he worked in a lab)... anyway, you can really focus bright light on an object - and guess what???? Under that light, it definitely glowed red. I looked at it next to the synthetic when the synthetic looked the reddest, so I could compare them side by side. While it doesn't show as red as the synthetic, it definitely is red ... YAY! I then put them both under short wave and long wave UV lights and the synthetic turned red under one and a chalky looking pink under the other (don't remember which was which) but the cushion didn't react.

I know that's not a deciding test, but it did make me feel a lot better. As a bonus, the other two stones show red under the filter also (YAY again). I just wish there was a "chelsea filter - filter" that you could put on your camera so a photo would show what I saw.

 

[VapidLapid]

some years ago i purchased some stones from ravenstein. All were touted as extremely rare world class museum quality investment grade stones. One was a yellow opal material type radiant cut from the faroe islands. another was a spess and a malaya. In all I think I paid twelve dollars, though that was far far more than they are worth. considering what they ARE worth however, they can ONLY increase in value. I hope you fare better with your cobalt spinel. I am concerened that fracture which surfaces at the girdle runs straight into the heart of the meatiest part one would want for a recut.

 

[colorluvr]

In two posts above, the last picture - side on of the cushion showing the inclusion - is excellent.

When you look through the loupe what does the inclusion look like? Does it look like a feather or a fingerprint or something completely different?

I couldn't really tell under the loupe, so I looked at it under the microscope and I would say between the two, it's probably a fingerprint. When you magnify it that much you see that it's not solid, and so looks more like the fingerprint.

LD,

I was checking out some cool inclusion sites and found a picture of an inclusion that looks like the one in the big spinel. Unfortunately, I shipped the stone off before I realized I could take photos through my microscope and also before the second lens arrived, so I didn't get a photo, but this one looks very similar. It is from the website geminterest.com. It's in French, but I used Google translate and it worked fine - this is a screen print, so it doesn't translate that well, but the photo can be found under inclusions, (upper left side) then spinel (group)

It looked like the inclusion in the upper right hand corner of this picture. There are some really good inclusion photos on this site.

When I get the stone back, I'll see if I can get some better photos of the inclusion.

 

[colorluvr]

Ok, I just figured out to get it to enlarge - here's a much better screenprint from the website.