AGTA TUCSON GEM AND MINERAL SHOW: FEBRUARY 4-9 2020
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PostPosted: Fri Sep 15, 2006 8:44 am 
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This company is coating other Gemstones as well and I'm wondering, as you pointed out that RI for CZ and diamonds are both beyond 1.80 or the GIA's 1.81 refractive liquid if a good way to spot this treatment is that the RI of a gem would be "offscale" due to the treatment?

Contrary to what is taught by some people, the gemmological refractometer indicates the RI of a stone due to TIR between the hemicylinder/liquid and the stone. So no matter how high the RI of the liquid and or hemicylinder is, you would still get the RI of the coating.
A Brewster Angle Meter wont help you for the same reasons (with TIR replaced by surface reflection).

For RB stones the dot or tilt tests are still a good indicators to see if it may be CZ, aswell as some other optical observations.


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PostPosted: Fri Sep 15, 2006 9:32 am 
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Hey Doos -- I should know this from your context, but what does TIR stand for?

Do you think the red dot &/or tilt test still apply for a CZ coated with diamond?

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 Post subject: sharp facets and RI
PostPosted: Fri Sep 15, 2006 10:47 am 
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Pt - thanks for clarifying the information about facet sharpness. I was hoping it would be a universal datum that could be used to Identify the treatment when applied to coloured stones

*shrug*

So guys how do we spot this treatment on coloured stones other than th efact that they seem to be impossibly brilliant.

Doos - I hope I have this straight

If a Tourmaline (RI 1.607 - 1.55), for example, was covered with this diamond treatment then the RI of the stone would show as (RI 2.417)
am impossibly high number for Tourmaline to have?

O h :oops: I too have no idea what TIR stands for

Thanks

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PostPosted: Fri Sep 15, 2006 10:58 am 
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TIR = Total Internal Reflection.

Wolf you are correct, it would give you an RI of 2.417 on the Tourmaline (if the coating has that RI).
I have no idea how it would react under a polariscope, but I'm sure it would be an interesting image. Immersion should reveal some things aswell.


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PostPosted: Fri Sep 15, 2006 11:51 am 
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Do you think the red dot &/or tilt test still apply for a CZ coated with diamond?


Yes of course Peter, well cut RB Diamonds fail the dot test due to TIR, the coating will have some effect on it but it will not create the TIR in the CZ. It just alters the path of the incident light a bit and probably increase the surface reflection on the Diamond/CZ layer at the table.
We could easily calculate the effect with the laws of refraction and reflection.

I'm sure anyone without a gemmological background would be very puzzled by all the abbrevations .. RB, CZ, TIR.


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 Post subject: thanks Doos
PostPosted: Fri Sep 15, 2006 12:06 pm 
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Thanks Doos:

That should help in spotting a Coloured stone with this treatment. :)

Impossibly brilliant and has an impossibly high RI.

Only problem is if as you say the optics may be "messed up" it might be impossible to identify what the original untreated stone was before treatment.

I know most here worry about diamonds but I am oriented more towards coloured stones. *shrug* Diamonds are nice and may be forever and *chuckle* a girl's best friend but coloured stones have more "romance" as they are still identifiable as having "come from" somewhere exotic rather than a DeBeer's vault :)

Well with the exception of "canadian diamonds" with that cute Polar Bear etched on the girdle :)

thanks

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PostPosted: Fri Sep 15, 2006 12:09 pm 
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No arguments on that one from me.


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PostPosted: Fri Sep 15, 2006 12:09 pm 
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I'm sure anyone without a gemmological background would be very puzzled by all the abbrevations .. RB, CZ, TIR.


You're right -- I'm fairly familiar with gemology and still get lost on occasion. Maybe we should compile a common acronym list for the links at the left. Something like the diamond terminology page.

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PostPosted: Fri Sep 15, 2006 12:19 pm 
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That's not a bad idea.
What do you think, should we have it on a seperate page, or right on the left below FREE GEMOLOGY COURSES.


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PostPosted: Fri Sep 15, 2006 12:23 pm 
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Maybe in a seperate "nerds abbrevation chart".


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PostPosted: Fri Sep 15, 2006 1:00 pm 
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Or maybe we should name it an "Introduction to the Inner Circle", with all the hodgepodge going on in here we could just as well start a sect! Wouldn't it be fun if we all stood on our toetips, chanting "May the sparkling heaven of TIR be revealed to us for our Enlightment, Divine Refractometer!" balancing at the pavillions of brilliants to get the inner feeling of a stone?
Anyway, good idea, who does?

Besides this, I wonder if it would be such a good idea to check the RI on a refractometer? As I've understood it, the surface coating isn't polished again after the process, wouldn't this mean that the surface will be somewhat raw and therefore easily could scratch the hemisphere if not handled very, very carefully?

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PostPosted: Fri Sep 15, 2006 1:11 pm 
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What do you think, should we have it on a seperate page, or right on the left below FREE GEMOLOGY COURSES.


I think a separate page would be best. I can't think of any at the moment, but there may be some overlapping abbreviations that need a little more explaination.

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PostPosted: Fri Sep 15, 2006 1:16 pm 
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OK.
I've started a list; I'll continue with definitions later today:
http://gemologyonline.com/acronyms.html

Please post ALL the acronyms you can think of and I'll try to get the list up by this evening. Thanks.
-Barbra


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PostPosted: Fri Sep 15, 2006 1:17 pm 
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Or maybe we should name it an "Introduction to the Inner Circle", with all the hodgepodge going on in here we could just as well start a sect!


Wait... we're not a sect? Then what was with all the pigeon blood ruby at midnight stuff they made me do before I could post?? :D

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PostPosted: Fri Sep 15, 2006 1:21 pm 
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Wise and excellent insights, PT.
Perhaps this page should be password protected. :wink:

PS I'll also eventually get in in alphabetical order. :oops:


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