Lapidary / Gemstone Community Forum

Stone Talk / Moderator, Hummingbirdstones ( Robin ) => Fascinating Facets => Topic started by: trigon on August 15, 2014, 04:18:24 pm



Title: Heat treating Montana Sapphires
Post by: trigon on August 15, 2014, 04:18:24 pm
Does anybody know the procedure for heat-treating Montana Sapphires? I have a bunch of them from some summer vacation days spent digging up at El Dorado Bar and Castles.

I remember seeing an old episode of Kirsten Gum's Treasure Hunter Show years ago and she was doing some digging down around Phillipsburg. They heat treated the stones she dug and as I recall, they were pretty open about how they did it. Of course, I didn't think to take notes and I can't find a copy of the old episode anywhere.


Title: Re: Heat treating Montana Sapphires
Post by: gemfeller on August 15, 2014, 04:27:51 pm
It's better to send them to a commercial heat-treater.  It's not usually a do-it-yourself procedure because it requires very expensive specialized ovens that take the corundum to near-melting temperatures, far higher than can be achieved by ovens for metal casting or ceramics.  Also, a different process is needed for treating sapphires from different localities due to differences in chemistry. 

There may be other suitable treaters but here's one I've used:  http://www.gemmountainmt.com/#!heat-treating/c1l2w



Title: Re: Heat treating Montana Sapphires
Post by: mirkaba on August 17, 2014, 08:34:53 am
It is really not worthwhile to heat treat Eldarado Bar/ Missouri River Sapphires as only 10 to 15 percent will be amenable to the treatment. Rock Creek /Phillipsburg Sapphires on the other hand treat very well. I just sent my 3 largest Eldarado Bar Sapphires off to be cut and I think I can live with the blue-green color. I also have 12 Small Yogos being cut. Can't wait to see how they turn out!  Good Luck :)


Title: Re: Heat treating Montana Sapphires
Post by: gemfeller on August 18, 2014, 11:29:37 pm
I also have 12 Small Yogos being cut. Can't wait to see how they turn out! 

That's really interesting.  How did you come by rough Yogo?  From what I read it's really difficult to come by because of tight restrictions by the leaseholders. 

Waiting for images!


Title: Re: Heat treating Montana Sapphires
Post by: mirkaba on August 19, 2014, 05:24:24 pm
I picked up about 500 carats of small yogos a few years back. When I sorted them I only had 30 or 40 stones that I thought were cuttable. Just sent some of the smaller stones to be cut in Thailand. They are very small but I am told they make saleable earrings. The larger stones should be done soon but it will be a while on the Thai cut stones will get some photos when they return. Photobucket is acting up again, I hope this works.....

(https://gemstone.smfforfree4.com/proxy.php?request=http%3A%2F%2Fi155.photobucket.com%2Falbums%2Fs287%2Fmirkaba%2Fyogos_zps4c052222.jpg&hash=7bc86dc6cb420baa6d2290ad5def1323) (http://s155.photobucket.com/user/mirkaba/media/yogos_zps4c052222.jpg.html)


Title: Re: Heat treating Montana Sapphires
Post by: navneetgems on July 06, 2020, 01:24:04 am
HT-P (High temperature Pressure) sapphires were started for treatment in 2009. This treatment is not an easy treatment to do, according to our research, its a treatment that is very similar to the standard Heat treatment that is available readily in the market and since the difference is little (Especially with Microscope the traits were similar to those of traditional heat (Lotus Gemology, 2019). Interesting that this sapphire treatment that is capable of doing permanent deformation of the sapphire lattice, in particular crystallographic orientation, not maybe in the entire direction. So you know some people might say, we are using a kind of press which pushes sapphires from all directions. Ceramics in general, including sapphires are resistant to compression, but they are not resistant to tension. This is a property of all material with covalent or ionic bonding. But if you pull it, it would break apart quite easily or show deformation. In terms of sapphires its not so important even though you apply compression from all sides, you will still have tension components at particular crystallographic direction, because its an anisotropic material.

You can check out Heat treatment video at https://www.youtube.com/watch?v=i4rb6u0V4-s&t=25s