Buyer beware!! Oiling of sapphires

[T L]

Beware of a newer treatment on sapphires, oiling.

"Oiling - An increasing number of sapphires treated with oil are appearing in the marketplace. Oiling the stone is a way to fill surface fractures. This treatment enables gem dealers to sell a larger stone (at a higher price) because fractures that might otherwise have to be cut away are filled with oil. Oil fillers are not stable and will evaporate over time, leaving a less attractive stone with readily apparent fractures."

"Ask whether the stone has been oiled. This treatment is coming into use and is often not disclosed by the gem supplier. Unless the jewelry retailer is a trained gemologist who has inspected the stone in a gem lab, he may not be aware that it has been oil treated."

Source:
http://jcrs.com/JCRS_for_consumers/jewelry_information/colored_gems/sapphire.htm""""

I know a vendor that had an oiled sapphire and when he submreged it in alchohol to remove the oil, all the inclusions showed up.

So, for sapphires, besides synthetics to worry about, we have the following treatments that I know of.

Regular heat
diffusion
irradiation
coating
fracture filling (now with oil, and maybe perhaps resin or wax, but not sure about the latter).

As always, buyer beware, and get that AGL report. The vendor above bought the sapphire from his supplier with a GRS report that indicated no treatment. He then sent it to AGL that deemed it oiled, so vendors are getting lab reports first, and then oiling the material, and sending them to customers as untreated. As always, the sapphire market is one of the scariest, especially with everyone wanting one for an e-ring these days. Evidently heat is not necessary for oiling either, or it is low heat that cannot be detected.

 

[Pandora II]

They've been doing that and fracture filling with resins for quite a number of years and not just sapphires - spinels, garnets, tourmalines, basically anything with a surface reaching fissure or fracture. Ruby is the most common one you find it in (I exclude emerald as it's an accepted treatment).

To be honest they are easy to spot - and not many people here are going to be buying stones with surface reaching fractures. Without those there is zero point in oiling as sapphires are not porous!

 

[Arkteia]

Thank you, TL! I have read a similar post and it scares me because it states that with time the stones start looking worse.

 

[Barrett]

Thanks for the info and update, TL
It's good you posted this!

 

[Imdanny]

 

[Quantz Studios]

To be honest they are easy to spot - and not many people here are going to be buying stones with surface reaching fractures. Without those there is zero point in oiling as sapphires are not porous!

With all respect, someone here could quite possibly purchase a stone with surface reaching fractures- ...if they cant see them clearly because they've been oiled.


Thanks for the info. Yet ANOTHER thing to keep an eye out for.

 

[LD]

I'm surprised that this isn't more widely known. Like Pandora, I've been aware that this has been around for several years.

What I am worried about, and hadn't even given it a thought, was that a gem could be sent for a lab report before this treatment and then the treated applied afterwards. I guess the time this wouldn't work is when the gem's photo appears on the report but even then the buyer could well just think it was a bad photo.

 

[Blue-Seeker]

Thank you for posting this information, TL. My question is, wouldn't there be a discrepancy on the clarity between the two reports, with the first report showing a lower clarity because of the fractures and the second report showing an improved clarity after the oiling?

 

[T L]

Thank you for posting this information, TL. My question is, wouldn't there be a discrepancy on the clarity between the two reports, with the first report showing a lower clarity because of the fractures and the second report showing an improved clarity after the oiling?

You're welcome.

I don't know. I don't think the AGL fast track report, which was obtained in the vendor's case, even mentions the clarity. You would need to obtain the more expensive Prestige reports for that.

 

[T L]

I'm surprised that this isn't more widely known. Like Pandora, I've been aware that this has been around for several years.

What I am worried about, and hadn't even given it a thought, was that a gem could be sent for a lab report before this treatment and then the treated applied afterwards. I guess the time this wouldn't work is when the gem's photo appears on the report but even then the buyer could well just think it was a bad photo.

I know, which is why people should always get their own independent verification on an expensive stone, no matter what it is. Some sellers are very honest, and will also send a gem out for you, after you purchase it, and that is fine with me as well. In fact, that is how this one vendor found the problem with the sapphire (he ended up selling it very low). If they have stones from their suppliers with very old lab reports, I would also get it checked out.

I worry about those sellers that are unscrupulous.

 

[chrono]

That's pretty sneaky - oiling after the the stone coming back from the lab. Some PSers might be able to detect it but I'm sure many others won't be able to, especially if unaware of such treatment of corundum that aren't in the red spectrum (ruby).

 

[Edward Bristol]

I think oiling is mostly done on cabochons.

 

[T L]

I think oiling is mostly done on cabochons.

I first noticed it on a faceted stone (it was in the GIA report) and the above mentioned trademember had found it on a faceted gem. Perhaps most cabs have oiling (????), but I wouldn't rule it out if it's a faceted gem.

 

[pregcurious]

Thanks, TL! I'm still relatively new to gems and had no idea.