Possibly fake large green spinel

[deuteriumhusky]

Hello, I scored this blue-green spinel from the son of a late gem collector and I'm fairly certain that it's fake given that the stone is 6.9 carats in weight and how uncommon the color is (green spinels are almost unheard of in jewlery) however I would like to have a second opinion from the people on this forum.

A few things make me think that the stone is natural:
The gem was measured with an Reflectometer by the seller and it's RI index was the same as natural spinel
Since green spinels are so uncommon it's possible that the gem cutter who faceted the stone purposely made the table too large in order to preserve gem material and increase the size of the stone.
If this was a synthetic stone, there would be far more material to work with, hence there's no need to cut the stone so that windowing would occur.

Here are some pictures of the stone in question: **Edited by moderator, no outside links please**

If this stone is real, should I have it re-cut it to mitigate windowing or should I keep it as it in order to preserve cutting material?
What are your general thoughts about the stone?

 

[chrono]

The stone screams synthetic to me too. A synthetic stone will have the same RI as a natural stone because they are made of the same material, the only difference is that one is made by humans and the other is made by nature. The lack of inclusions is also troubling and I've seen plenty of poorly cut synthetics. Before doing anything else, I would want more testing done to make sure it is a natural stone.

 

[VapidLapid]

Much as I would love to gawk at a fake green spinel, I, and many others are understandably unlikely to click on an unknown outside link in a member's first and only post. it is very easy to upload your photos directly to this thread. You also might want to ask the moderators if a discussion about synthetics is permitted.

 

[deuteriumhusky]

Here are pictures of the stone in question.

 

[chrono]

Since the stone hasn't been determined to be synthetic (yet), I think we can still discuss it. Also, as I have foolishly clicked on the link this morning, I might as well help post the pictures.

ETA
OP has posted them, so I won't double post.

 

[deuteriumhusky]

Has anyone seen a spinel of this coloration before? I'm considering taking it to a local gemologist.

 

[chrono]

I would not bother with a local gemmologist unless he has more tools than a refractrometer and is experienced with coloured stones other than a sapphire. Polariscope and an understanding of the inclusions viewed under high magnification will be helpful.

 

[deuteriumhusky]

Where would you recommend I take it to then?

 

[chrono]

Are you in the US, Europe or Asia? My preference is a good lab because they have many more tools on hand with experience that is difficult to replicate.

 

[deuteriumhusky]

I'm in the US, typically how much does it cost to get a stone looked at, I'm fairly new to the world of gemology.

 

[Marlow]

The stone screams synthetic to me too. A synthetic stone will have the same RI as a natural stone because they are made of the same material, the only difference is that one is made by humans and the other is made by nature. The lack of inclusions is also troubling and I've seen plenty of poorly cut synthetics. Before doing anything else, I would want more testing done to make sure it is a natural stone.

VERY LOUD!!!

Agree - size, color and the cut - looks like a synthetic spinel used as an alternative for
aquamarine.

If Verneuil they often have a higher RI ( 1,728-1,740 ) course a bit more Aluminium. It funny but the higher Al content will produce an aqua- color using Cr!!!! and Cobalt - chrome red synthetic spinel are only red if MgO : Al2O3 is 1:1

 

[chrono]

You missed the 4.99 ct cut-off mark for the $60 AGL gem brief, which leaves you with the $140 Prestige Report option.
http://aglgemlab.com/pricelist

GIA also offers their service at $120
http://www.gia.edu/gem-lab-service/colored-stone

 

[T L]

Has anyone seen a spinel of this coloration before? I'm considering taking it to a local gemologist.

I have, but only in synthetics. That's probably what it is if it is spinel.

 

[deuteriumhusky]

I'm looking at the stone right now and there appear to be these thin needles that go in multiple directions? Is that a giveaway that it's a synthetic?

 

[chrono]

There are several types of synthetics and each type has its own characteristic inclusions; there is flame fusion, flux-melt and Czochralski (pulling).

 

[deuteriumhusky]

The needles look exactly like these:

 

[chrono]

Are you sure that you are not mistaking them for the hollow tubes seen in flux spinels? I do not possess a microscope so powerful as to be able to see the inclusions as shown in the picture you linked.

 

[deuteriumhusky]

I might be mistaken though. These inclusions extend through out the entire length of the stone and they're straight. They go in multiple directions though. Most likely the stone is a synthetic in my opinion.

 

[FrekeChild]

This stone looks EXACTLY like a synthetic spinel I used to own...

http://loupetroop.com/listings/rings/filligree-ring

Sorry there aren't more pics of the stone posted, but my guess is that it is man-made.

 

[T L]

Here's another, similar color.

http://www.rubylane.com/item/996295-440/Arts-Crafts-Sterling-Silver-Synthetic-Spinel