Apatite treatment

[ccgems]

Does Anyone know how to heat treat facet-quality Apatite rough? I bought some great dark teal colored Apatite rough, but would like to lighten it up. I know heating is possible, but I''d like to know how? Temperature? Length of time? etc...

 

[lelser]

Date: 12/3/2009 9:33:35 PM
Author:ccgems
Does Anyone know how to heat treat facet-quality Apatite rough? I bought some great dark teal colored Apatite rough, but would like to lighten it up. I know heating is possible, but I''d like to know how? Temperature? Length of time? etc...

Apatite is generally NOT heated, and I''m unaware that it lightens or changes tone with treatment. It''s sensitive to thermal shock, and usually has inclusions that make heating unpleasant

It''s been known to fracture on the dop if the heat gets too high and is one of those stones you keep a finger on while cutting.

My recommendation is to use brightening cuts - the RI is high enough to give you options - and not try to heat anything you aren''t prepared to lose.

Cheers,

Lisa

 

[morecarats]

Date: 12/3/2009 11:03:05 PM
Author: lelser

Date: 12/3/2009 9:33:35 PM
Author:ccgems
Does Anyone know how to heat treat facet-quality Apatite rough? I bought some great dark teal colored Apatite rough, but would like to lighten it up. I know heating is possible, but I''d like to know how? Temperature? Length of time? etc...

Apatite is generally NOT heated, and I''m unaware that it lightens or changes tone with treatment. It''s sensitive to thermal shock, and usually has inclusions that make heating unpleasant

It''s been known to fracture on the dop if the heat gets too high and is one of those stones you keep a finger on while cutting.

My recommendation is to use brightening cuts - the RI is high enough to give you options - and not try to heat anything you aren''t prepared to lose.

Cheers,

Lisa

I believe this information is incorrect. I deal a fair bit in Madagascar apatite, and all of the neon blue apatite is produced by heat-treating the green apatite. I''m sorry I don''t have any technical information on the specific heating conditions. I''ve observed the process, but I''m not a gem burner myself and don''t know the secret for achieving that wonderful paraiba-like blue.

 

[lelser]

Date: 12/3/2009 11:21:03 PM
Author: morecarats

Date: 12/3/2009 11:03:05 PM

Author: lelser

Date: 12/3/2009 9:33:35 PM

Author:ccgems

Does Anyone know how to heat treat facet-quality Apatite rough? I bought some great dark teal colored Apatite rough, but would like to lighten it up. I know heating is possible, but I''d like to know how? Temperature? Length of time? etc...

Apatite is generally NOT heated, and I''m unaware that it lightens or changes tone with treatment. It''s sensitive to thermal shock, and usually has inclusions that make heating unpleasant

It''s been known to fracture on the dop if the heat gets too high and is one of those stones you keep a finger on while cutting.


My recommendation is to use brightening cuts - the RI is high enough to give you options - and not try to heat anything you aren''t prepared to lose.


Cheers,


Lisa

I believe this information is incorrect. I deal a fair bit in Madagascar apatite, and all of the neon blue apatite is produced by heat-treating the green apatite. I''m sorry I don''t have any technical information on the specific heating conditions. I''ve observed the process, but I''m not a gem burner myself and don''t know the secret for achieving that wonderful paraiba-like blue.

That''s interesting. I spent time in Mada, and did buy some neon blue Apatite there, but was told they were not heat treated. Experiments with some greens of my own didn''t turn the shade although I was basically trying what works with tourmaline.

If you do get any details, I''d be very interested to know. The death rate on stones must be something awful!

 

[Gailey]

Date: 12/3/2009 9:33:35 PM
Author:ccgems
Does Anyone know how to heat treat facet-quality Apatite rough? I bought some great dark teal colored Apatite rough, but would like to lighten it up. I know heating is possible, but I''d like to know how? Temperature? Length of time? etc...

Welcome to Pricescope Ccgems. Can''t help you with your question, but maybe Gene Flanigan from Precision Gems will chime in. He heats stones I believe.

Nice avatar by the way.

 

[morecarats]

The Thai burners who treat this stuff (and sometimes bring it back to Madagascar) guard their secrets pretty closely. Not surprising really, since it''s a very lucrative business.

I understand that the secret to avoiding fractures in heating apatite has to do with the rate at which the temperature is increased during the heating process. Apatite is quite sensitive to sudden temperature changes, so increasing the temperature gradually is key. Sorry I don''t have any technical details on the recipe, but Ted Themelis in Bangkok offers practical courses on gem treatments and is willing to share his knowledge (for a price).

 

[chrono]

This is definitely interesting. I’ve always thought that apatites have been untreated. I suppose as with most heating, that one should be able to tell the heated and unheated ones apart under microscope?

 

[morecarats]

Yes, I believe heat treatment of apatite can be detected by gemological labs. It might be difficult with very clean specimens, but completely clean apatite is rare (unlike, say, aquamarine). Another variable is the temperature used; if the color change was produced at relatively low temperatures it would be harder to detect.

I checked with some of the dealers here in Thailand and sites like AJS and Gemselect disclose their neon blue apatite as heated. The asparagus green apatite is unheated.

 

[chrono]

MC,
Thanks for the update. However, considering the inexpensive price of apatite, it’s really not worth the money for those in the USA or Europe to send their stones to labs for testing/certification.

 

[morecarats]

Chrono, I agree. I think you can just assume that, like blue zircon, the neon blue apatite has been heat treated. Most dealers will disclose the treatment.

 

[ccgems]

Hi all,

Thanks for the comment on my avatar. Its a new concave cut from my cutters in China. Its called a "Tai Chi" cut.
Re: the heat treatments of the Apatite I asked about...I do have one piece of absolutely gorgeous Paraiba Blue Apatite that I bought in Tucson in the rough. I do know that the rhat piece of rough had been heated. I have heard many things, from the heat process has to be very slow...to the fact that the heating process has to be done via a vacuum. I don''t know exactly which is true. But I do have about 200 grams of fairly clean rough that I know can be lighten, just wish I knew the process.

 

[chrono]

Joe,
Do you have larger picture of the Tai-chi concave faceting of that stone? What gemstone is it?

 

[lelser]

I''ve got an 89ct piece of neon Mada rough bought in Mada, which does not look heated to me based on the condition of the (very small) inclusions. I''m going to take it into the lab when I do my next run and have it tested and will report back. It honestly doesn''t effect my appreciation of the stone, and since it should cut to over 20 cts will be expensive enough to justify testing.

Cheers,

Lisa

 

[ccgems]

Here is a closer look at the Tai Chi Cut and the stone is Citrine.