Processes

[Opallover]

What is the difference between BE treated and Heat treated stones?

Linda

 

[colorchange]

There are a number of heat treatments :
- Traditionnal Ceylonese low heat treatment will bring temperatures around 400°C for, say, one hour. Will hardly alter inclusions, often goes unoticed at a lab. I have tried today to take photos of very slightly altered rutile in a Ceylon pad, that is very typical.
- Modern heat treatment is rather around 800°C and lasts longer.
- "New Heat Treatement" that involves lead glass or flux to fill fissures : affects the price very very seriously.
- Berylium Heating or HTLE (HeaTing with Light Elements) at soime labs. That involves very high temperatures (sapphire almost melts) and adding some color (diffusion of color)
- There are now a niber of other diffusion that involve creating a star, and blue color, but until now blue color is restricted to the surface.

Unfortunately, the first 2 kind are not separated by labs... though the first kind of treatment traditionnaly sells for around the same price as untreated, so it is now quite difficult for the client to make the difference : some dealers will bring to every lab until one don't see the evidences of heating...

 

[Richard M.]

Date: 3/18/2006 9:29:38 AM
Author:Opallover
What is the difference between BE treated and Heat treated stones?


Linda

Hi,

The subject of gems and gem treatments isn''t easy (for me at least) to explain simply or quickly. Like all learning a certain amount of ''homework'' is required on the part of the student.

Since Richard Hughes and Bill Larson of Pala Gems have gone to the trouble to create these ''lessons,'' let me recommend them to you for your first assignment. When you''ve studied them, get back to us with questions. You''ll probably have plenty.

Lesson 1: Hughes

Lesson 2: Larson

Happy studying!

Richard M.

 

[Opallover]

OK, so let''s say the stone that I bought iscoming from Chanthaburi, Thailand but originated in Madagascar, where actual pads come from Sri Lanka. So more than likely my stone which they say is heat treated may actually be of this controversial heating that not a lot of people know about. In talking about a orgne rim around pink sapphre, can this be seen with the naked eye or a loop? Also, since a lot of these studies were done 4 years ago in 2002, could things have changed in the heat treatments of these stones? And wasn''t Thailand at the discussions?

Since purchasing this stone, my curiosity is really racing and now I want to learn more.

Linda

P.S. Thanks Richard. You always give me good advice. Any books that you could recommend?

Linda

 

[strmrdr]

There are plenty of good books on gemstones out there but even the best are out of date on treatments the day they are printed.
Vincent''s website is the best resource Iv seen for keeping up to date on them.
I dont have a link right now on this computer but Im sure someone can post it.

 

[strmrdr]

links:
http://www.fieldgemology.com/

http://www.aigslaboratory.com/

 

[Richard M.]

Date: 3/18/2006 10:38:53 AM
Author: Opallover
Since purchasing this stone, my curiosity is really racing and now I want to learn more.
Linda
P.S. Thanks Richard. You always give me good advice. Any books that you could recommend?

Storm''s right that Vincent Pardieu of AIGS is one of those on the leading edge of corundum treatment.

I think Ted Themelis, who himself conducts seminars on corundum treatment, has probably published as much on that specific topic as anyone. His website with book list is Here His book "The Heat Treatment of Ruby and Sapphire" is one I can heartily recommend. He also has written several others on this subject. And Richard Hughes''s "Ruby & Sapphire" is indispensable in learning about corundum.

Yes, the white hats are always playing catch-up with the black hats, but it''s very important to know the history of the topic. A point that''s usually overlooked is while corundum seems to be the focus of interest, the majority of gems offered for sale are somehow treated/enhanced/synthetic. Diamond is increasingly subject to lab treatments. Some minor examples in colored gems: lapis is sometimes dyed and waxed; most citrine began its life as amethyst before heating; a huge portion of amethyst offered for sale is synthetic; white topaz is irradiated and heated to turn it blue while quartz goes through the same process to manipulate its color centers to yellow-green, and on and on. Topaz is probably the most lab-manipulated stone of all. It''s diffused, coated, irradiated and heated into a huge range of colors, some found in nature, others not.

That''s one of the reasons I specialize in garnets and a few other stones I know are entirely natural. I sell others, of course, because there''s demand but prefer to tell customers the stone they buy is just as nature made it.

This is a huge, complex subject and you''re not going to learn about it quickly by reading a book or two, Googling to find what often turns out to be misinformation, buying a few stones and becoming an ''expert,'' as many try to do. You need grounding in mineralogy to understand what gems really are and how they differ from one another. You need to know a little chemistry and physics, then have a basic understanding of the principles of gemology: specific gravity, index of refraction, spectrum, optics (single and double refraction, pleochroism) etc. I''ve been at it more than a few years now and learn important new things every day.

Richard M.

 

[colorchange]

Date: 3/18/2006 10:38:53 AM
Author: Opallover
OK, so let's say the stone that I bought iscoming from Chanthaburi, Thailand but originated in Madagascar, where actual pads come from Sri Lanka. So more than likely my stone which they say is heat treated may actually be of this controversial heating that not a lot of people know about. In talking about a orgne rim around pink sapphre, can this be seen with the naked eye or a loop? Also, since a lot of these studies were done 4 years ago in 2002, could things have changed in the heat treatments of these stones? And wasn't Thailand at the discussions?

Since purchasing this stone, my curiosity is really racing and now I want to learn more.

Linda

P.S. Thanks Richard. You always give me good advice. Any books that you could recommend?

Linda

You stone is indeed most probably from Tanzania or maybe Australia that produces most of the low quality sapphires.
They are often presented as from Madagascar because some true pad comes out in Madagascar, that are just as good (or vey near to) as those from Ceylon !
The best indicator that is went through this treatment is price... you just don't sell a pad for that price !!!!
The other one is that the seller sells soooo many orange-yellow and pad colored sapphires that they may just not be natural, the whole world must not produce that many heat-only sapphires of these colors. A few monthes ago he was selling one yellow sapphire VVS over 5 CT per day, that's just not realist !

Regards

Henri