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Torbernite (Natural Uranium)

Posted: 11 Jun 2019, 08:10
by Go-Figure
Hi folks,
This weekend I received a sample of Torbernite from Congo (actually it was shipped to me from France, but I was told the sample was originally from Congo).
As usual I first tested I with the Geiger counter (always wearing gloves, never touching the sample directly and cleaning everything afterwards to avoid inhalation or ingestion), the result was pretty stunning, 107000 CPM, by far the highest read I've ever got on my geiger counter.
But, having to do with Uranium before, I learned this doesn't necessarely mean an equally impressive level of gammas would materialise as well.

I did three tests on the sample. Almost at contact at first, and then at 5 and 10 cm. The results showed below are the ones from the first test (at contact).
The spectrum is very rich, with three peaks I never caught before, two from Bismuth 214 at 1509 and 2204 keV, the latter being much more evident in the energy per bin view.
The third one is not really clear, is around 13-14 keV, there's really no clear hint of it in the spectrum, but I have a gaussian correlation there, besides it shows much more clearly in the tests at a farther distance, so in the end I decided to "call it".

In terms of dose (I think it would be more correct if I just said exposure here) the result is pretty high, roughly ten times the background at contact (actually at 1 cm, being 1 cm the approximate distance from the detector housing to the actual crystal), but still not even close to the Pentax lens I test a couple of weeks ago, which remains the hottest object I tested so far https://www.gammaspectacular.com/phpBB3 ... ?f=5&t=519

Talking about the quantitative aspect I have to add that my previous analisys contained a wrong figure for the crystal weight, which (according to the estimate Steven gave me not long ago) should be in the region of 380 grams, instead of 300.

The figure mentioned above reduces to roughly 3 times the background at 5 cm and it's comparable to the background at 10 cm.

It was a lot of fun testing this one and also it made for some interesting close photos!

Massimo

Re: Torbernite (Natural Uranium)

Posted: 11 Jun 2019, 10:24
by Steven Sesselmann
Massimo,

Thanks again for an excellent post, I commend you for your consistency and attention to detail.

I notice you are operating close to 2000 cps, which must be close to the limit of what your sound card can count, but from your three comparisons above it looks as if you are not loosing too many counts. What was the dead-time on these experiments, and did you correct for it ?

Re: Torbernite (Natural Uranium)

Posted: 12 Jun 2019, 03:00
by pilgrim
Great post and very beautiful sample of Torbernite : did you try to light It with a UV light?

Re: Torbernite (Natural Uranium)

Posted: 12 Jun 2019, 07:56
by Go-Figure
Steven Sesselmann wrote:
11 Jun 2019, 10:24
Massimo,

Thanks again for an excellent post, I commend you for your consistency and attention to detail.

I notice you are operating close to 2000 cps, which must be close to the limit of what your sound card can count, but from your three comparisons above it looks as if you are not loosing too many counts. What was the dead-time on these experiments, and did you correct for it ?
Thank you for an excellent detector.
Yeah, this one was pretty hot, but not the hottest I tested so far. The Pentax lens alone was 2230 CPS after subtracting the background, it was 2500 CPS including the background, so I know the counts can get at least as high as that before hitting the limit.
I didn't correct for it this time, but I plan to repeat the test on the hottest samples in order to see what difference it makes.
I have all data in another computer, but I rememeber the dead time was about 145 μs.
Great post and very beautiful sample of Torbernite : did you try to light It with a UV light?
Actually I didn't. I have a book called "Introduction to Radioactive Minerals" by Robert Lauf and it says Torbenite exibits no UV fluorescence. But since you asked I thought to give it a try and...it doesn't fluoresce. I have other ores which do.

Re: Torbernite (Natural Uranium)

Posted: 03 Jul 2019, 13:11
by Conor Whyte
Here is a sample NORM spectrum from my iRad rebuilt Sionix detector of Uraninite.


Btw, we have a few places here in BC that are hotspots for Torbernite, Autunite, Uranophane...
I'm going on a Uranium and rare-earth mineral hunting journey at some point this summer.
Intend on getting get lots of samples (that's the plan).


-- Yes, Torbernite is not fluorescent in UV at all. I can second that. Actually no copper uranium minerals can react under UV.
Autunite, Uranocircite, Uranophane, Zippetite and Andersonite all exhibit distinct fluorescence. There are probably a few more to add to this list.
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