How to tell natural from synthetic sapphire?

[pokerface]

As I posted in an earlier thread ([URL='https://www.pricescope.com/community/threads/two-big-sapphire-cabochons-one-gray-star-one-blue.210253/']https://www.pricescope.com/community/threads/two-big-sapphire-cabochons-one-gray-star-one-blue.210253/[/URL]), I have purchased a blue sapphire cabochon that was advertised as natural, unheated and untreated.

I understand that given the price, it is unlikely to be as advertised. However, to me, the stone does not appear to be obviously a total dud - if it did, I wouldn't have bought it in the first place.

I'm taking the stone into an appraiser next week who will be able to identify if the stone is synthetic. I thought it might be fun to make a poll before I learn the real answer.

I am also hoping that people will comment as to hallmarks that may identify a sapphire such as this as natural or synthetic.

Thank you!

Here's the ebay listing with pics and video: http://www.ebay.com/itm/291349717259?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

And hand shots:

 

[treasurehunter]

A shot of the base please?

Usually magnification is the test to separate synthetic and natural sapphires

 

[marymm]

Pure guesswork, based on pics/listing - if it was actually lab-created, I would expect it to have better color/clarity - and it seems to have a color and strange schiller effect I don't associate with untreated sapphires - so I voted "No - otherwise treated". Still, for the price, whether treated or synthetic, I think it is pretty in appearance.

 

[minousbijoux]

Fwiw, here is toolhaus's feedback: http://toolhaus.org/cgi-bin/negs?User=ploysuaygems14&Dirn=Received+by

I think its mighty nice looking, and looks great on your hand. Would you still wear it if it was synthetic?

 

[pokerface]

How specifically can magnification distinguish a natural sapphire from a synthetic one?

Here are some shots of the base:





The Schiller effect referenced by marymm is strange - it seems like the cabochon is almost a star sapphire, but not quite.

What makes me lean toward thinking the sapphire is synthetic is that 1) the base is flat and 2) the sapphire has strange inclusions that could potentially be curved growth lines.

I put the sapphire on a flashlight and then snapped this shot of the inclusions:

 

[minousbijoux]

Where's Marlow when we need him? Check out the website with "gemology" and "online" in the title, or check out The Gemology Project which has all sorts of info on inclusions and growth lines in synthetic corundum.

 

[treasurehunter]

magnification is the required test for testing synthetic sapphire vs natural

gas bubble and Curved growth bands are a sign of flame fusion sapphires which are the most cheap synthetic and common
Usually this can be found easily on the base

angular growth at 60 and 120 degrees is a sign of natural

the other option is its not even syn sapphire it could be glass or dyed quartzite

Its hard to see in the photo what it looks like really,

 

[Marlow]

Could be everything....

The last picture shows a concentration of color in fractures.

Dyed glass or sapphire??? Don't know....I voted for treated sapphire looking at the backside of the cab.

Put it in Acetone or Alcohol for a while - then youwill see what happens ( Blue Curacao? )

BUT

We have to be careful...

There is a quarz cab in a GIA article - looks manmade with bright red inclusions.

It is cinnabar in quarz!!! Outstanding!!! But in a show if not offered from special vendors like the Gemtrader I would never buy...

Scroll down till Figure 10!

http://www.gia.edu/cs/Satellite?blobcol=gfile&blobheader=application%2Fpdf&blobheadername1=Content-Disposition&blobheadername2=MDT-Type&blobheadername3=Content-Type&blobheadervalue1=attachment%3B+filename%3DGG-Gem-News-International&blobheadervalue2=abinary%3B+charset%3DUTF-8&blobheadervalue3=application%2Funknown&blobkey=id&blobtable=GIA_DocumentFile&blobwhere=1355958114096&ssbinary=true

 

[LoversKites]

Wow the quartz in that article is awesome.

 

[Marlow]

But looks "artifical" or not...

 

[pokerface]

So good news - the appraiser was able to identify the stone as natural corundum. He said if it was heated, it was done so at a very low temperature, because he was able to see fine needles. He also said that he was not able to tell if the sapphire was dyed (can't easily test for dye without destroying the stone), but his instinct was that it is not dyed. He said that it is a low grade stone, so not worth submitting to an official lab for a report. I am definitely happy with the outcome - I didn't get ripped off with my purchase, and I find the sapphire to be very pretty - well worth my $20.

 

[Marlow]

So good news - the appraiser was able to identify the stone as natural corundum. He said if it was heated, it was done so at a very low temperature, because he was able to see fine needles. He also said that he was not able to tell if the sapphire was dyed (can't easily test for dye without destroying the stone), but his instinct was that it is not dyed. He said that it is a low grade stone, so not worth submitting to an official lab for a report. I am definitely happy with the outcome - I didn't get ripped off with my purchase, and I find the sapphire to be very pretty - well worth my $20.

OK

How did he identify the cab as a corundum - RI is difficult course you have to be able to use the spot method... only for experienced gemmologist ( and they would be able to check it for dying )????

You have done a very good shot - the last one with stroooong light from the side. Color concentration like shown in your pic is typical for dying - the color "follows" the cracks. So a maybe pale blue was dyed to get this deeper blue color.

You payed 20 for this stone or this appraisal???

But this is only my opinion.....

Spot method = No table facet or other one so you get no line using the refractometer - only a small contact on the glass plane - a lot of try and error to see a small dot around 1,762 - 1,77 ( for corundum).

 

[Marlow]

I am a pain in the ....

Look at the original pic in the middle - from 11 to 1 you see a strong concentration of color - looks like a bird and two wings with stronger color line and then the fracture is paler ( sorry can't explane it better... )

Maybe somebody can post the pic....

 

[pokerface]

I am in NYC, and I visited a very credible GIA gemologist. He obviously was able to see the color concentration, but as I said, his best guess was that it was in fact natural. Dyed or not dyed, the stone is not worth much as the crystal is not well-formed. I am fully confident in the appraiser's ability to test for corundum. I specifically asked if he could test for dye, but he said that he couldn't without damaging the stone (or perhaps there is a more expensive test that just wouldn't have been worth it).