Irradiated gemstones

[morecarats]

It is well known that virtually all the blue topaz in the market has been irradiated and then heated. But there are often rumors that specimens of other gems varieties owe their color to irradiation, including tourmaline, kunzite, hiddenite, beryl, imperial topaz and zircon.

However, irradiation is one of those treatments that are extremely difficult to detect, and even the best gem labs won''t be able to tell you if your gem has been irradiated. So what to do if you''ve got a stone that you suspect was irradiated?

You could try a test that gem dealers use to check for irradiation. The test may be destructive, so don''t try this with a stone that you''re not willing to discard.

Take a photo of the suspect gem under controlled conditions and then put the stone in direct sun for a couple of days. This works best if you live in a location with strong sunlight such as Thailand. Then photograph the stone again under the same lighting conditions and compare the before and after photos. If you detect significant color loss you probably have an irradiated stone. In many cases an irradiated stone will lose its color entirely.

If you don''t want to try this with one of your valued gems, you can obtain test material from eBay that is likely to produce a positive result.

 

[chrono]

MoreCarats,
Wouldn’t this be inconclusive with kunzite and possibly some other gemstone variety that has a tendency to fade under sunlight anyway?

 

[morecarats]

It is unclear whether the kunzite that loses color when exposed to light does so because it is in fact irradiated. We have performed this experiment with kunzite that did not lose color.

However, even the test is not reliable for a few light-sensitive varieties, it may still be helpful in many other cases. It is particularly useful when unusual material suddenly comes on the market, such as the saturated "patroke" kunzite that was being pushed on TV.

 

[T L]

What about heated tourmalines? Is there a way that a lab can determine if a stone is heated? I have some Mozambique tourmalines that have needles, and I believe they have been heated to cuprian blue colors, but the needles are still there, unlike rutile needles that dissipate when a sapphire is heated for example.

 

[morecarats]

Paraiba tourmaline is typically heated, but heated at temperatures that are not high enough to dissolve inclusions. That is why gem labs are generally unable to tell whether a tourmaline (beryl, spodumene, apatite, etc.) have been heated. Sapphire, by contrast, is heated at very high temperatures (over 1600 C) and the effects on internal structures are visible under a microscope.

 

[VapidLapid]

what about the radiation? aren''t irradiated gems radioactive long after treatment? Isn''t that why the DOE banned them from US? If they are then wouldn''t that be readily detectable with a geiger counter? Is deep blue color in topaz ever possible without radiation? would that color itself be diagnostic of irradiation? can a stone that responds to heating and that is heated be heated again with good result? (thus eliminating the possibility of a response to heating indicating no prior heating)

 

[morecarats]

Date: 6/3/2010 8:13:40 PM
Author: VapidLapid
what about the radiation? aren''t irradiated gems radioactive long after treatment? Isn''t that why the DOE banned them from US? If they are then wouldn''t that be readily detectable with a geiger counter? Is deep blue color in topaz ever possible without radiation? would that color itself be diagnostic of irradiation? can a stone that responds to heating and that is heated be heated again with good result? (thus eliminating the possibility of a response to heating indicating no prior heating)

The lighter blues in topaz are irradiated with linear accelerators and there is no residual radiation soon after treatment. The darker blues such as the so-called london blue are irradiated in nuclear reactors and must be held for some months before they are safe to release to the market.

The DOE has not banned blue topaz from the US, but irradiated topaz entering the US is now supposed to be tested (and some of it probably is).

If a sample of some gem variety is heated with no result one can conclude only that (1) it doesn''t respond to heating or the specific heat treatment attempted; or (2) it had previously been heated. I doubt gem labs will start heating stones as a way of trying to determine whether they were heated. For one thing, if the gem had not previously been heated, the owner now has a heated stone, exactly the result he was hoping to avoid.

 

[VapidLapid]

I was imagining the heating trial more as a test of the probability or not of treatment in a parcel of rough, than diagnostic in a finished single stone. A few weeks ago when I was looking into the treatment of zircons I found some articles that discuss a second heating in zircons and it being effective in lightening color After an initial heating had already been performed. If there are no tests for heating of zircon BUT the stone can only respond to one heating then heating one exemplary stone in a parcel of stones all collected same time place source...then IF that stone responded to heating one could say that there is likelihood that the parcel is unheated. BUT if the stone could respond to heat treatment a second time then even this imperfect test of a parcel could not indicate anything.

 

[T L]

Morecarats,
Thank you for answering our questions. Are tourmalines typically heated before they''re cut or after, or it doesn''t matter.

 

[T L]

Date: 6/3/2010 8:25:00 PM
Author: morecarats

Date: 6/3/2010 8:13:40 PM

Author: VapidLapid

what about the radiation? aren''t irradiated gems radioactive long after treatment? Isn''t that why the DOE banned them from US? If they are then wouldn''t that be readily detectable with a geiger counter? Is deep blue color in topaz ever possible without radiation? would that color itself be diagnostic of irradiation? can a stone that responds to heating and that is heated be heated again with good result? (thus eliminating the possibility of a response to heating indicating no prior heating)

The lighter blues in topaz are irradiated with linear accelerators and there is no residual radiation soon after treatment. The darker blues such as the so-called london blue are irradiated in nuclear reactors and must be held for some months before they are safe to release to the market.


The DOE has not banned blue topaz from the US, but irradiated topaz entering the US is now supposed to be tested (and some of it probably is).


If a sample of some gem variety is heated with no result one can conclude only that (1) it doesn''t respond to heating or the specific heat treatment attempted; or (2) it had previously been heated. I doubt gem labs will start heating stones as a way of trying to determine whether they were heated. For one thing, if the gem had not previously been heated, the owner now has a heated stone, exactly the result he was hoping to avoid.

I was reading about this. There are two types of bombardments, ones with neutrons, and the other with electrons. I believe the electron bombardment is safer.

 

[morecarats]

Date: 6/3/2010 9:53:36 PM
Author: tourmaline_lover
Morecarats,
Thank you for answering our questions. Are tourmalines typically heated before they''re cut or after, or it doesn''t matter.

I have heard that tourmaline is sometimes heated but despite living for many years in a center for gem treatments, I have yet to meet anyone who heats tourmaline. The gem burners I''ve asked about it tell me that they don''t heat tourmaline because it tends to crack when heated.