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missing bastnasite

Posted by James Christopher  
avatar missing bastnasite
August 18, 2012 01:18AM
us    
Lost in the mail, or stolen, 1 to 2 of the bastnasites in this photo, not sure which ones, vanished on their way back to me from Skip Simmons recently. They have areas of high Nd content, and may be actual Bastnasite-(Nd). If anyone sees any of these for sale, please let me know.
Re: missing bastnasite
August 18, 2012 06:34PM
at    
James: the Ce L beta1 peak strongly overlaps with the first Nd peak (Nd L alpha1). Thus, the spectrum clearly shows a Ce-dominant phase.
See also [www.kayelaby.npl.co.uk].
avatar Re: missing bastnasite
August 19, 2012 12:24AM
us    
Jim,
You gave me the 3 shown below prior to shipment to UNO.
Did all of these show the internal zoning along with an anomalous Specific Gravity?

Uwe,
Would you be willing to share your 1997 publication with Jim and myself?:
"Untersuchungen über die Seltenerden-Carbonate Bastnäsit und Synchisit von der Grube Clara im Schwarzwald: Nachweis von Bastnäsit-(Ce), Bastnäsit-(Nd), Bastnäsit-(La) und Synchisit-(Ce)."

Regards,
Dean Allum





Edited 2 time(s). Last edit at 08/19/2012 06:32PM by Dean Allum.
avatar Re: missing bastnasite
August 19, 2012 04:48PM
us    

Here are clearer photos. I can understand what you are saying Uwe, but it appears Skip has clearly marked the L1 Ce line as well as the Nd line. In the high Nd sample, the L1 Ce line appears lower, and it is indeed the Nd line which is tallest(spot 3). Another area, spot 2, has higher Ce. The high Nd area also appears more opaque, and has much lower La than the Ce sample. But clearly Skip didn't want to outright call it Nd dominant, and you two are clearly much more knowledgeable on the subject than I am. Skip is a well respected geologist who has been studying rare earth pegmatites since at least the 1970's, and works at the University of New Orleans
avatar Re: missing bastnasite
August 19, 2012 05:16PM
de    
"Skip is a well respected geologist [...]"

If he also was a respected analyst, he would have sent you a summary of his interpretations of the experimental results - instead of leaving it to his customers to make unqualified assumptions ...
Re: missing bastnasite
August 19, 2012 05:51PM
at    
Dean: I have no PDF version of the article (in German) but I could send you the *.doc version.

Some further comments on the spectra:
- "... and it is indeed the Nd line which is tallest(spot 3)" The "Nd" peak is a sum of the mentioned Nd and Ce peaks; simplified, the Ce beta peak has to be subtracted from the Nd peak to get the real height.
- The software should provide a list of wt.% and/or atom% contents of the elements. Did you get only the spectra?
- The spectra are rather noisy
avatar Re: missing bastnasite
August 19, 2012 05:56PM
us    
I assume a more detailed report was included with the samples, but I can ask Skip for the numbers assuming he still has them.
One other important fact in finding them, is they all have a core of fluocerite, they are not pure bastnasite crystals.
avatar Re: missing bastnasite
August 20, 2012 05:40AM
us    
Ok, I guess it was my misunderstanding as to how he was analyzing it. He did it for free and apparently only did a qualitative EDS, no WDS, so no numbers as to percentage. So unless I get further analysis proving otherwise, I guess it is Bastnasite(Ce) with a high Nd content.

"There are no actual numbers. We ran a qualitative analysis which only shows the identity and relative abundance of the elements in the sample. This information was meant to give you an idea of what your samples were. They are not meant to be published on the internet or used to provide a definite confirmation of the mineral identity or composition of a rather complex rare earth element mineral. So I caution you about using the data for any other purpose. I teach a semester long course on the use of energy dispersive spectrometry and spend a lot of time demonstrating why EDS spectra and most software packages that are used on SEM instruments cannot reliably obtain accurate quantitative results on rare earth minerals. The hundreds of analyses that we have published on rare earth minerals have been done using the electron microprobe which can be used with proper standards to provide quantitative analyses. These analyses are time consuming and expensive to obtain and we only use this instrument for our research projects. I know there are a number of labs that for a fee provide standard-less EDS analyses with numerical results, but our lab has checked some of these result from a couple of labs and found the results to be only approximate at best. Finally to underscore the difficulties of rare earth mineral analyses, I had a student do a master’s thesis on the spectral overlaps and corrections necessary to properly analyze rare earth minerals.

To learn more I recommend the book: Electron Microprobe Analysis and Scanning Electron Microscopy in Geology by S. J. B. Reed. "
Re: missing bastnasite
August 20, 2012 01:09PM
It makes sense that it would be Cerium dominant. Basnasite-(Ce) is a common alteration product of fluocerite-(Ce). Most of the Little Patsy fluocerite-(Ce) occurs with a thin reddish surface of bastnasite -(Ce). Yours just went through a more thorough process. A specimen of bastnasite crystals surrounding a core of fluocerite was found in Crystal Park, El Paso County in 1880, by a local prospector. It weighed 7 kg! I believe this piece went to the Smithsonian. Neat find anyway. Not an easy thing to come across in any Colorado peg.
Re: missing bastnasite
August 20, 2012 01:56PM
at    
Dean: file sent.
avatar Re: missing bastnasite
January 16, 2013 01:10PM
us    
It appears they never even made the mail. I got an e-mail the other day stating a package was coming my way from the University. Should be here today or tomorrow. Yay for happy endings!
avatar Re: missing bastnasite
January 16, 2013 11:41PM
us    
Guess I spoke too soon. I got something I bought off e-bay, ironically from the same guy who was to mail my bastnasites back.



Edited 1 time(s). Last edit at 01/17/2013 03:01AM by James Christopher.
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