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PostPosted: Sun Aug 02, 2009 8:10 am 
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10-4
have a good friend which is a radiology tech - they have to wear a badge which monitors how much radiation they have been exposed to. :wink:


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 Post subject:
PostPosted: Mon Aug 03, 2009 7:47 pm 
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gingerkid wrote:
10-4
have a good friend which is a radiology tech - they have to wear a badge which monitors how much radiation they have been exposed to. :wink:


Yup, I used to be a surgical asst. for a veterinarian in college. I had to wear the badge and they would test it so often. I always took the best, and therefore most pics so my reading was always higher than everyone else. Now, when I turn off the lights now my hands glow a nice blue apatite color. :lol:


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 Post subject:
PostPosted: Mon Aug 03, 2009 10:32 pm 
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my best friend is a scrub nurse/surgical technician. she loves it. i don't think i could touch half the folks to prep them for surgery, even wearing surgical gloves, with a 10-ft pole, lol! i wish i would have gone to school to be a vet tech, not too sure about the surgical assistant though.

instead, i received a diploma in medical assisting, then got side-tracked with working part-time and paying for 2 years of college. i would have to go back and do clinicals over to be able to work as a medical assistant. :cry:


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 Post subject: detect irradiated blues by chelsea filter
PostPosted: Mon Aug 03, 2009 10:45 pm 
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Barring detectable radioactivity, is there any test to distinguish irradiated blue topaz (any kind, Sky, Swiss, London) from natural blues?

rom,

irradiated blues appear pink(ish) through a chelsea filter. the deeper the colour, the stronger the reaction. so this works particularly well with swiss and london blue, might fail with sky blues.

then, of course, you don´t need any test to detect swiss and london blue as the colour is telltale

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 Post subject:
PostPosted: Mon Aug 03, 2009 11:50 pm 
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hi gemtrader,
i tried to find information/research on differentiating irradiated blue topaz (swiss, london, sky) from the natural blue topaz.

cannot find anything, except something about a "fade test," in which the stone will fade in color due to unstable color, ? not too sure if this is in clear stones irradiated to the blue color (?), or what the truth is to be honest and totally confused.

hopefully, one of our knowledgeable and experienced gemmo members will share how they distinguish irradiated blue topaz from the natural ones.


:wink:


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 Post subject: Re: detect irradiated blues by chelsea filter
PostPosted: Tue Aug 04, 2009 12:54 am 
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gemtrader wrote:
rom,

irradiated blues appear pink(ish) through a chelsea filter. the deeper the colour, the stronger the reaction. so this works particularly well with swiss and london blue, might fail with sky blues.



What was the source of natural blue topaz you used as the control in this filter study? Do you have any data on filter reactions to it? Did you use natural blue topaz from more than one source? Naturals are pretty scarce but have been reported from Russia, Brazil, Australia, the USA, Nigeria and probably other locations.

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 Post subject: Re: detect irradiated blues by chelsea filter
PostPosted: Tue Aug 04, 2009 12:54 am 
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gemtrader wrote:

irradiated blues appear pink(ish) through a chelsea filter. the deeper the colour, the stronger the reaction. so this works particularly well with swiss and london blue, might fail with sky blues.


I've never heard this before. Of course, I'm not a fan of using a Chelsea Filter for anything.

In nature topaz occurs in yellow, yellowish brown, pale blue and colorless.
When most topaz is subjected to irradiation it will turn a cinnamon brown. This color is unstable and fades quickly but often, if this cinnamon brown topaz is heated after treatment, it will change to a stable blue color. There are also some nuclear reactors which can produce a blue color without subsequent heating.

Most of the properties of natural blue topaz are identical to artificially created blue topaz. It is entirely possible that natural blue topaz was created in the same way that artificial blue was created. To my awareness, the color center for blue topaz has still NOT been identified.

The difference then is only in the length of time in which these processes occur. In nature, topaz is subjected to low levels of radiation over very long periods of time, whereas in artificially irradiated topaz, the gems are exposed to massive amounts of radiation in a short time. This effects whether or not the electron traps in the topaz are occupied or not and cause the stones to react differently when tested for thermoluminescence.

This is the only method that I am aware of for determining natural vs. irradiated blue. It is beyond the scope of standard gemological testing, not to mention that the extreme heat the topaz is subjected to causes it to bleach out, so only small scrapings are usually tested.

I think most of us just presume that if the topaz is blue, it has been artificially irradiated. If someone is representing a topaz as a natural blue, I would put the burden of proof on THEM and insist that the stone be accompanied with an identification report from a lab with proper testing equipment.


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 Post subject:
PostPosted: Tue Aug 04, 2009 2:33 am 
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gingerkid wrote:
10-4
have a good friend which is a radiology tech - they have to wear a badge which monitors how much radiation they have been exposed to. :wink:


Yep. It's called a TLD or Thermoluminescent Dosimeter.

Image

This is a pocket ion chamber used to record daily cumulative radiation manually. Your responsibility not the laboratory.

Image

They also have personal alrming dosimeters that enunciate an alarm when a pre set level of exposure is reached. Good to have if you anticipate rapidly changing conditions and when the PAD alarms, it's time to get out of Dodge. :wink:


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 Post subject: chelsea filter study
PostPosted: Tue Aug 04, 2009 4:24 am 
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during an extensive chelsea filter study, conducted in the early 90ies on a private collection of more than 1000 stones, from actinolite to zoisite, 11 specimens of blue topaz, 6 of which were of natural blue, were tested in an austrian trade lab.

the natural blues came from australia, brazil, zimbabwe and nigeria.
one natural blue was of unknown origin and we also tested a few natural blues from russia which came from my stock.

filter reactions on the natural blues were:
australia: 1 weak green
brazil: 1 weak green, 1 weak brownish,
1 very dark blackish blue stone from brazil was inert
nigeria: very weak brownish
zimbabwe: weak green

i do not remember the exact reactions of my natural blue russians as they were not part of the study and thus not noted. unfortunately i have sold them all...

irradiated blues were quite new at the time, so the collection held only five specimens, all london blue, if i remember correctly.
the filter reaction of all irradiated specimens was a weak to distinct brownish red.

since then i have routinely looked at many swiss blue specimens trough the filter and the reaction always is a weak to distinct pink, depending on colour intensity.

so, to get things straight: the chelsea filter is inadequate to separate natural blue from irradiated blue topaz.
you don´t need it to identify london blues and swiss blues and with sky blues the raction is very weak, if any.

however, if you are in doubt whether a ligt blue stone is an aquamarine or something else (intense sky blue or light swiss blue topaz), have look through the filter. if you see pink, you know at least that it´s no aqua.

beware: a light blue gem showing a pink reaction might also be synthetic spinel.

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 Post subject:
PostPosted: Tue Aug 04, 2009 4:14 pm 
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hey guys and gals,

I remember someone saying that some of the fake imperial topaz is simply irradiated to give it that salmon-orange color and that if it's exposed to sunlight it'll fade pretty quickly. But, why doesn't that happen to the typical blue topaz? It's irradiated too, right? Is it a different type of radiation used?


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 Post subject:
PostPosted: Tue Aug 04, 2009 4:36 pm 
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"But, why doesn't that happen to the typical blue topaz? It's irradiated too, right? Is it a different type of radiation used?"
=================

robertb,

...they use better glue :smt114


bear


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 Post subject: Re: chelsea filter study
PostPosted: Tue Aug 04, 2009 5:37 pm 
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gemtrader wrote:
during an extensive chelsea filter study, conducted in the early 90ies on a private collection of more than 1000 stones, ...

Perhaps someone should mention that between then and now, the Chelsea Filter was changed, without notice. :( Now, it transmitts more light than it formerly did. How that affects the color one sees, I don't know. :?:
I just thought I would mention it to stir up the pot a bit. :lol: :lol:
Quote:
however, if you are in doubt whether a ligt blue stone is an aquamarine or something else (intense sky blue or light swiss blue topaz), have look through the filter. if you see pink, you know at least that it´s no aqua.
beware: a light blue gem showing a pink reaction might also be synthetic spinel.

I see the Chelsea Filter is still looking for a use, since no one is faking emeralds with green glass anymore.
The Aquafilter was designed for characterizing blue stones, and it does. :D :D


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 Post subject:
PostPosted: Tue Aug 04, 2009 7:14 pm 
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how long do they "treat" the london blue topaz?


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 Post subject:
PostPosted: Tue Aug 04, 2009 7:28 pm 
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Since this topaz conversation has ranged far and wide I feel justified in sticking this in.

Image

This is being offered to me as a Brazilian natural blue topaz, 2.7kg.

Somewhat interesting, never had natural untreated blue topaz before, what do people think?

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 Post subject:
PostPosted: Tue Aug 04, 2009 7:44 pm 
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it's lovely, john, wonder if it's au-natural?? :wink:


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