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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 @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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