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61
EPMA Standard Materials / Re: Geophysical Lab Probe Standards
« Last post by Probeman on July 18, 2024, 07:32:35 AM »
Several people responded but Andrew gave a very informative reply:

Hello,
The attached paper of MacGregor (1974) mentions EnAl-5, EnAl-10, and EnAl-15 in his Table 1, and mentions them again as glasses in the Starting Material section of his Appendix. The Acknowledgments mention a fellowship ath the Geophysical Lab and also thank Dr. F.R. Boyd.

Marinenko (1982) in Table 3 of NBS Special Publication 260-74 describes “ENAL 10 – from Geophysical Laboratories)”, “a synthetic glass”, with the same composition, but presented as elements rather than oxides.

P-140 is apparently olivine from the Balsalm Gap dunite in North Carolina.

A typewritten letter, headed Finland, April 20, 1971 from H.B. Wiik (Hugo Birger Wiik of Finland) to F.R. Boyd gives the composition of the olivine (which includes 0.13 Al2O3).  In my photocopy, this letter is annotated with a handwritten note: “Zies give 7.28 Fe as FeO”.   The exact same analysis of Wiik is reproduced in Table J on page 17 of the PhD thesis P.J. Lawless (Cape Town, 1978).

My researches on P-140 in 2016 yielded:

The material may have been collected by Hess, and a hand-specimen is described in detail in the appendix of:

Davis, G.L. and Hess, H.H., 1949. Radium content of ultramafic igneous rocks; II, Geological and chemical implications. American Journal of Science, 247(12), pp.856-882.

The wet-chemical analysis was performed by E.G. Zies of the Geophysical Laboratory, according to a footnote to Table 2 of:
Boone, G.M. and Fernandez, L.A., 1971. Phenocrystic olivines from the eastern Azores. Mineralogical Magazine, 38, pp.165-78.

This olivine analysis was apparently reported by F.R. Boyd of the Geophysical Laboratory, according to the supplementary Table A1 in the appendix (p. 13) of:
Hofmeister, A.M., Xu, J., Mao, H.K., Bell, P.M. and Hoering, T.C., 1989. Thermodynamics of Fe-Mg olivines at mantle pressures: Mid-and far-infrared spectroscopy at high pressure. American Mineralogist, 74, pp. 281-306.

http://www.minsocam.org/msa/ammin/Supplemental_Data/Vol%2074%20p0281%20AM-89-400.pdf

Finally, a partial analysis of this same olivine is found in Table 2 of:
Jarosewich, E., Parkes, A.S. and Wiggins, L.B., 1979. Microprobe analyses of four natural glasses and one mineral: an interlaboratory study of precision and accuracy. Smithsonian contributions to the earth sciences, 22, pp.53-67.

Based on the literature references that I have found, it appears that the P-140 Balsam Gap olivine (forsterite) was used as an electron microprobe standard at the following, in addition to the Geophysical Laboratory:

-              Chicago (Mason et al., 1982);
-              MIT (Jarosewich et al., 1979);
-              Yale (Boone and Fernandez, 1971).

In addition to the notes about sample P-140 in Davis and Hess (1949), I did note that in the Carnegie Institution of Washington Year Book No. 46 (published 1947) it was reported (p. 38) that about 1000 pounds of the Balsam Gap dunite were collected.

I corresponded with Shaun Hardy at Carnegie, who inspected Dr. Zies’ notebooks and research files, and Dr. Boyd’s correspondence and research files, but no luck with regard to Balsam Gap olivine.  Shaun put me in touch with the Smithsonian (Leslie Hale), but no documentation was available.

Finally, my own analyses of the P-140 olivine in the University of Alberta lab do not show the same high Al contents. I suspect that the analysis of Wiik was by wet chemistry, and perhaps contaminated with some amount of clinochlore or some such.

I hope that this information proves useful to you.

Best regards,
Andrew

Andrew Locock, PhD
EPMA Lab Manager

Dept. of Earth and Atmospheric Sciences
Room 1-26 Earth Sciences Building
11223 Saskatchewan Drive NW
University of Alberta
Edmonton, Alberta, Canada T6G 2E3

Tel: 780-492-3191
Fax: 780-492-2030
www.eas.ualberta.ca/eml/
www.microprobe.ca
62
EPMA Standard Materials / Geophysical Lab Probe Standards
« Last post by Probeman on July 18, 2024, 07:30:30 AM »
John Fournelle and Anette asked the following on the Cameca listserver:

Quote
This is a history-of-microbeam-standards quiz question for the _really_ old timers out there (you know who you are). Anette found these both in the Smithsonian’s back room files as well as at the University of Minnesota.

The Carnegie Probe Lab (at the Carnegie Geophysical Lab in DC) provided series of EPMA starndards to several labs, probably in the 1970s and on a bit. We are looking for someone to provide some more details. Who developed and send out these materials? Was it Joe Boyd? They include both natural and synthetic (including WEF14, DJ35, ENAL series, doped Diopside glasses). This is a poorly recorded/reported part of our history.

John and Anette






63
Discussion of General EPMA Issues / Re: Using fityk to determine flank positions
« Last post by Probeman on July 17, 2024, 07:07:13 AM »
For others interested in the Flank method, please search for "flank" in this user forum to see more on this method. For example:

https://probesoftware.com/smf/index.php?topic=1605.msg12395#msg12395
64
EPMA Sample Preparation / Re: EPMA Sample Preparation Discussion Board
« Last post by Probeman on July 17, 2024, 06:57:12 AM »
Any thoughts on resin/hardener brands? The current mixture we are using results in epoxy mounts that contain sulphur which is a pain when measuring apatite.

My favorite epoxy is "Petropoxy" which is sold here:

https://www.burnhampetrographics.com/petropoxy/ppp.php

It's stay liquid until heated so give one a long working time which is useful for complicated mounts like this:

https://probesoftware.com/smf/index.php?topic=172.msg12595#msg12595
65
Discussion of General EPMA Issues / Using fityk to determine flank positions
« Last post by Ben Buse on July 17, 2024, 04:38:45 AM »
Hi

As I've just tried this I thought I'd write it down, in case of use to anyone else

(1) Load program
(2) Data > Load File (For PFE .dat export file - enter column numbers for x and y - in this case x 23 y 33) > Open slot > Click on each file & repeat open slot (4 andradite repeats, and 4 almandine repeats)
(3) Select 4 andradite repeats - go to Data > Merge Points - output to new dataset
(4) Repeat for 4 almandine repeats
(5) Data > Edit transformations - add new function to normalise data e.g.
Code: [Select]
y=y[n]/max(y)*100 and apply to both merged datasets
(6) Create difference spectra - type in command line
Code: [Select]
@+ =@10-@11 where10 and 11 are the spectra numbers

(7) Duplicate Difference Spectra (see sum button)
(8.) Fit peak to the maximum difference and identify centroid giving a flank position - it only fits peak to positive values so shift spectra to positive values using edit transformations - add new function
Code: [Select]
Y=y[n]+25 - using data-range mode deselect parts of spectra not relevant to fitting - select split pearson7 - auto-add - start fitting - either write down centre of fitting peak (the flank position) or Functions>Export peak parameters

(9) Duplicate Difference Spectra (see sum button)
(10) Fit peak to the minimum difference and identify centroid giving a flank position - use Data > Edit Transformations > Invert - to make negative peak a positive peak - select region for fitting - fit and record peak position as before

66
EPMA Sample Preparation / Re: EPMA Sample Preparation Discussion Board
« Last post by Alejandro Cortes on July 17, 2024, 12:03:17 AM »
Any thoughts on resin/hardener brands? The current mixture we are using results in epoxy mounts that contain sulphur which is a pain when measuring apatite.
67
EPMA Standard Materials / Re: Unsure of Analysis Standard
« Last post by crystalgrower on July 15, 2024, 11:53:39 AM »
You could try simply using the stoichiometric composition of 29.95% C and 70.05% Si.  Use this to see what you get for SiO2 and CaCO3 in-house. 

But as you can see (attached) using EDX would give false C results regardless of how many phases are or are not present.  ONLY SDD can give an accurate EDX analysis for C. 

With respect to this business of phases, it is not worth your time.  It would be more cost effective to go to a jeweller and buy moissanite SiC which is definitely the octahedral phase. 
68
DTSA II / Re: "Strip background" by using Clayton's algorithm
« Last post by ZhaiQ on July 12, 2024, 10:54:35 PM »
Hi Prof Ritchie,

Thanks for your answer about the algorithm. Meanwhile, may I consult what is the formula DTSA uses to "fit spectra"? Is it polynomial equation? Thanks!
69
EPMA Standard Materials / Re: Unsure of Analysis Standard
« Last post by mjpavel on July 12, 2024, 10:18:16 AM »
I appreciate the further insight! We have both powder and single crystal XRD so it may be something worth looking into for us. I think we're just going to go shop around another provider and see if someone has a product we can put some trust in to.

SiC is quite hard to work on even by XRD given so many polymorphs. It is supposed to be a line compound and precipitate out the C or Si depending on what side of the phase diagram you are on, but subtle changes in the C/Si ratio push you into other polymorphs and there is some questions about the stoichiometry of those other polymorphs and is there vacancy ordering etc etc.....

I'm interested enough in the problem that I may sink some time into taking a TEM / atom probe lift out and looking into it further (although each of those have issues too). I think our other possibility is to verify it ourselves using APF factors and pure material standards that we have...Honestly all comes out to the same point - I didn't get what I thought we got
70
Cameca / Re: very low counts in standards
« Last post by Probeman on July 12, 2024, 07:15:07 AM »
While our Jeol is being repaired I decided to venture in the cameca instrument we also have for the first time. I am experiencing issues with counting on standards. Peak positions are found effectively but retrieving less than 2k cts. While for Si (Spec 4 TAP-Albite) and Na (Spec 2 LTAP-Albite) this is fine, Al is really bad (Spec 4 TAP - Corundum). I though this had to be with column alignment but then why is it good for some elements and bad for others... Any input will be greatly appreciated.

That sounds like spectrometer alignment issues to me.   

Usually this requires a service engineer but if you have instructions it can be done by any competent technician.  For alignment of TAP spectrometers one first vents the instrument, then removes the spectrometer covers and all column separation windows (of the low pressure spectrometers) and replace them with Mylar windows. Then pump the column down again, but leave the covers off the spectrometers so they are at atmosphere. One then utilizes high order reflections (i.e., Fe ka 4th order) to perform the spectrometer alignments.

Be careful to keep your hand out of the x-ray beam coming through the Mylar windows!
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