tsavorite heat treatments

[MlMGeoGem]

Hello, I have been seeking after a natural, untreated tsavorite and recently heard from a gem dealer that all tsavorites these days are heat treated right at the mine sites and then sold to consumers as "natural". This is very concerning to me and I am wondering if this is truth or myth?? If anyone has any insight on this topic I would greatly value your time...as my objective is to find an untreated tsavorite in the 1-2ct size range for my custom engagement ring. Thanks to all in advance who respond

 

[PrecisionGem]

I have been to one of the tsavorite mines in Tanzania. I have never heard of tsavorite being treated, much less at the mine. The only heating I saw there was in this cook house, and I fear the chicken was going in the pot, not any stones.

This one stone was the only facet grade stone found for some time at the mine. There was a lot of low grade material and cab material found. These stones are very rare. Good luck in your search.

 

[VapidLapid]

Tsavorite Crusted Chicken!

mmm mmm good!

 

[RedSpinel]

From what I have heard over and over again over the years, garnets and spinels are not heat treated because, unlike many other gems, those 2 dont respond to heat treatment, as it doesnt improve or change their color. I have never heard of tsavorites being heat treated or chemical treated. Maybe they have come up with some new treatment that I am not aware of........

Thats one of the main reasons I am a fan of garnets and spinels is the fact that they are natural. What you see is what came out of the ground. They dont start out as cloudy brown stones that have chemicals pressed into them using heat and pressure in order to completely change their color to something more desirable. Thats not to say I dont like gems that are heat or chemical treated, but I'd prefer something that isnt. I own some sapphires that are yellow and golden and orange that are treated.

 

[MlMGeoGem]

Thank you to everyone that has responded to my tsavorite post thus far, I really value the input and shared knowledge! I too have never previously heard of tsavorites(*or garnets for that matter) needing heat treatments). So the gem dealer I heard from today who claims all tsavorites are heat treated at the mines had me very unsettled.

Again, I would certainly value any opinions on this subject matter......and otherwise welcome comments on whether using tsavorite for a center stone in an engagement ring is acceptable.

 

[MlMGeoGem]

Thank you ever so much for sharing your opinion!

 

[chrono]

I first heard rumours of heated tsavorite way back in 2007 but nothing was proven. Firstly, garnet cannot take high temperatures unlike corundum. Secondly, heating supposedly does little to improve colour. Clarity enhancement, however, isn't new or unheard of.

Red Spinel,
Garnet and Spinel can no longer be assumed to be untreated. Some spinels are now heated and oiled to improve clarity. Some garnets are now also fracture filled with resin to improve clarity. Unfortunately, these treatments are often times not disclosed to the buyer.

 

[MlMGeoGem]

Hmmm.....undisclosed fracture filling is very unsettling indeed. Is there no real way to protect the interest of the gemstone consumer nowadays?? Is such fracture filling not detectable by microscopic or other means of examination??

 

[chrono]

Fracture filling is detectable through examination under microscope, but you need to know what to look for.

 

[LoversKites]

From what I know demantoid is sometimes heated -- I've noticed it mostly in the Ural ones. I wonder why only demantoid though.

 

[chrono]

Because when they tried heating it, the colour improved. There wasn't much improvement in other garnets, so there were no returns for the treatment. One has to also be aware that demantoids can also be clarity enhanced with resins and a few have been found to be treated as such.

 

[LoversKites]

I worded my question badly. I meant why would the colour only improve in demantoids and not other garnets? Whatever the reason it's probably too complicated for me to understand

 

[chrono]

The reasons and methodology are apparently still highly guarded secrets. It seems that only a particular deposit of Russian demantoid are heated at a low temperature (speculated to be around 250 F ) to drive off a brown mask on the stones. So far, GIA is unable to tell the difference between naturally or artificially heated stones...I think, although there is discussion that it might be detectable via high magnification and study of the horsetail.

http://www.palagems.com/demantoid_disclose.htm

I'm not sure why heat doesn't improve other types of garnets though, other than it has to be the chemical makeup.