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Confusing Chromophores Can Confuse Gemmos
https://gemologyonline.com/Forum/phpBB2/viewtopic.php?f=86&t=19620
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Author:  Stephen Challener [ Wed Apr 16, 2014 3:03 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

@Barbra: thanks, and nice to meet you as well! Nice site you have here :D
@Bill: Thanks, that means a lot coming from you!

Author:  Stephen Challener [ Sun Apr 05, 2015 2:07 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

A couple of interesting things I came across in the GIA's gemology project:
Chrome diopside with Cr peak but no V peak in EDXRF (0.91 ct Pyroxene (Diopside) - Chrome Diopside from Kenya (PDF)
All four peridots examined showed significant nickel peaks as well, which isn't much help since one is a nice Burmese green, one is an Arizona yellow-green and two are Egyptian stones somewhere in between.

Author:  Bill Hanneman [ Sun Apr 05, 2015 5:08 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

Scarodactyl wrote:
Chrome diopside with Cr peak but no V peak in EDXRF

What were the reported relative sensitivities of Cr and V in that analysis?

Author:  dchallener [ Mon Apr 06, 2015 6:44 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

Hi Bill -
Reading in the paper I see this: https://s3.amazonaws.com/gubelin/pyroxe ... -35385.pdf says "Our EDXRT method can detect most elements with higher atomic numbers than sodium (Z=11) in the Periodic Table; depending on the element, the lower limit of detection is between 1 and 100 parts per million (0.0001 to 0.01%)."

I note that there were two peaks in the graph for Chromium and none for Vanadium. and I also note the atomic number of vanadium is 23. (Chromium is 24).

I am not sure if this is what you were asking for, but it seems like it might be?

another paper here:http://www.icdd.com/resources/axa/vol42/v42_17.pdf has information about EDXRF in general whit detection limits for both Chromium and Vanadium:
has this:
Table 1. EDXRF
Element EDXRF Detection Limit (ppm)

Antimony 3
Arsenic 4
Barium 10
Cadmium 2
Chromium 8
Lead 5
Mercury 9
Nickel 5
Selenium 2
Silver 2
Thallium 6
Vanadium 20
Zinc 2

Author:  Stephen Challener [ Mon Apr 06, 2015 9:43 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

I'm not an expert in edxrf, unfortunately. It's not really quantitative without further info, and the above post seems to indicate its a bit less sensitive to V for some reason. So clearly I can't guarantee from this that there's no V present, but that's not really the point. This stone is most likely Cr colored at least in part.

Author:  dchallener [ Tue Apr 14, 2015 6:59 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

a quick search on google came up with this quote:
Chrome-diopside is one of the main minerals contributing to this anomaly, having an average Cr content of 1505 ppm.

from this paper:
http://www.researchgate.net/publication ... ate_Brazil

If that is typical, then a sensitive to vandaium of 20ppm would surely have showed up if it were a major contributor to color.

Author:  ClassyCarat [ Thu Oct 29, 2015 3:46 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

I realize I'm on the late side here. The issue is that of chrome titanite (sphene) specifically from Pino Solo in Baja, Mx. Many years ago I personally collected and cut a decent sized chrome sphene from this site. I was sure I had done an absorption spec on this stone in the past. Moments ago, I confirmed. My stone definitely shows broad band far UV and far IR extinctions common to chromium. Although some locales for sphene may not have chromium as the chromophore, I submit that the Pino Solo material definitely does.

Author:  Stephen Challener [ Thu Oct 29, 2015 6:30 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

I suspect that it is almost or entirely always true that any mineral that accepts vanadium as a chromophore will also accept chromium, though the color produced obviously isn't always the same. The two elements so similar in size and charge it's hard to imagine a crystal lattice being willing to accept one but not the other. The only example I can think of off the top of my head where there isn't much acknowledgement of V as a chromophore where Cr is implicated is topaz, though there are mentions of it here and there.

Author:  Isi [ Fri Oct 30, 2015 5:27 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

Is there vanadium in rubies ?

Author:  Stephen Challener [ Fri Oct 30, 2015 6:35 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

Vanadium does act as a chromophore in sapphire, as seen in the ever-popular purple-pink color change synthetics. Not identical but broadly similar in color.

Author:  Nathan Renfro [ Fri Oct 30, 2015 8:40 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

Isi wrote:
Is there vanadium in rubies ?


Sometimes

Author:  Bill Hanneman [ Fri Jan 08, 2016 7:53 pm ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

There is a little bit of everything in everything. One must consider the limit of the detection of the method being used.

Author:  Barbra Voltaire, FGG [ Sat Jan 09, 2016 12:38 am ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

Sidebar: I have been told there is a trace amount of gallium in every natural ruby*.

*University of Heidelberg

Author:  Dan&Sally [ Mon Jan 18, 2016 1:02 am ]
Post subject:  Re: Confusing Chromophores Can Confuse Gemmos

AWSOME timing! Just read this chapter in the colored stones curriculum. We have to do something about this language barrier though. Does Rosetta Stone teach chemistry as a second language?

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