Gamma Spectroscopy to Differentiate Radioactive Minerals

[NVdesert]

I am new to gamma spectroscopy and trying to figure out whether it would be of value for my mineralogy applications. I have a question for individuals who might have taken spectra on several naturally occurring radioactive mineral species.

Most naturally occurring radioactive mineral species, at least the ones I deal with, contain the (UO2)2+, uranyl ion. I currently employ fluorescence spectroscopy on those minerals that fluoresce to help discriminate species. Most uranyl species display a characteristic 3-peak spectra, not unlike what is obtained with gamma spectroscopy. Although they are all uranyl species, there is a subtle shift between these peaks that can be used to fingerprint species. Also, there are sometimes characteristic distortions to these peaks (lopsided, double-peaks) that are useful to discriminate species. I have often wondered if the shift and/or shape of these peaks has something to do with minute quantities of secondary isotopes in the species, or the decay products that are present. I am aware that "on paper", all uranyl species should pretty much produce the same spectral profile with gamma spectroscopy.

1. Has someone taken gamma spectra on different mineral species and noted any differences in the profile? I should add that gummite and pitchblende are mineral amalgamations and not true mineral species. I would really like to hear from someone that has taken spectra on several reasonably pure mineral species. Common examples would be uraninite, torbernite, autunite, carnotite, etc.

2. Has anyone noted differences in the spectral profiles of the same mineral species, say uraninite, from different localities? Compositional analysis can sometimes be used to determine the origin of a mineral sample. Perhaps isotope fingerprinting with low-cost equipment might also be possible.

3. If either of the above two questions are true, what type of equipment are you using? In particular, the scintillation probe type?

Thank You in advance, for any input.

[Sesselmann]

Hello I trust your real name is not NVdesert,

Great question, but would you mind hopping on to the Introductions forum and giving yourself a brief introduction, it should technically be your first post..

The answer to your question is not simple, sometimes mineral samples might have different ratios of Thorium and Uranium, but I'm no expert on mineral analysis, so hopefully someone else knows more about it than me.

Steven

[NVdesert]

Hello Steven,
Sorry for the oversight, I missed the now obvious "Start Here!" when I joined the forum. I will take care of this now.

Storm S., from Nevada

[Madmax]

Hi NVdesert,
Do you have any exact task like "these two species should be distinguised between each other in-field in 5 minutes using gamma spectroscopy technique" or similar? Can you send samples of species to Australia?

Have a nice day!

Maxim

[NVdesert]

Hello Maxim and thank you for your reply.

I wouldn't be attempting to differentiate these uranyl species in the field. Thus, integration time for the spectroscopy measurement is not an issue. I would bring the specimens back from the field, sort them under magnification, and then trim them down to obtain as pure of a sample of the species of interest as possible before taking readings.

If you would like to attempt to take some readings on several species, to see if differences can be noted, I would be happy to provide some samples. I have species on hand such as andersonite, francevillite, and tyuyamunite that have full coverage on the face of the specimens; thus, insuring strong emissions from a single species. I would provide labeled, trimmed samples that would fit in a 1" square plastic "Perky" box. I think I can also provide samples of the same mineral species from different localities, which might be an interesting test as well.

Let me know.

Best Regards,
Storm S.

[Madmax]

Hi Storm,
So, what can i do to start: after receiving samples i can acquire gamma spectra using different spectrometers (at least CsI(Tl) 8 cm3, NaI(Tl) 40*40 mm (50 cm3) and LaBr3 25*25 mm (12 cm3) with resolution close to 3%). I will send all these spectra to you and will help with interpretation, or publish it here - maybe other people will find anything interesting. After that you can decide if scintillation gamma spectrometry is useful for you or not, and choose proper gamma spectrometer for your needs. Please drop me a message to max (at) gammaspectacular (dot) com, and I will reply with the address.

Have a nice day!

Max

[Marco75]

Hi Storm,
I am a radiactive mineral collector, not only an amateur of nuclear physics.
There is no way for example to discriminate an uraninite from a gummite or a uranocircite from an autunite or a torbernite or any other combination of uranium or thorium minerals. Every uranium minerals will show the same peaks created by the daugthers of U238 (Ra226, Bi214 and Pb214 mainly)
You can see differences due to the age of the sample or contaminations by thorium
The can distinguish a radian-barite because there is no U238 but only Radium and its daughters.

The same for Thorium minerals: with only the spectrum you can say that this is a thorium mineral, but not the type

what you can distinguish is of course a thorium mineral from an uranium mineral or the level of percentage of thorium/uranium inside for example in a Uraniumthorianite.

below an example: uraninite above, torbernite below (the two spectra do not have the same energy calibration).