stamasd - 30-9-2021 at 01:58
How often is 232Th present in uranium ores? I can't find much data to answer this question.
The reason I'm asking this is: I was recently using my gamma spectroscope to look at a sample that was given to me of supposedly an uranium ore from
Utah. And while there are peaks belonging to many of the decay products in the uranium series, there is also a significant peak that I cannot
attribute to any of those; the only possible isotope that would make that peak is 228Ac, and that one belongs to the thorium series.
unionised - 30-9-2021 at 09:56
Thorium is quite likely to be present in uranium bearing rocks.
They both have a stable (IV) oxidation state and the ions are about the same sizes.
(in one sense it's inevitable; the uranium decay series include thorium isotopes)
You could buy a rock (or gas mantle) that contains thorium to check.
stamasd - 30-9-2021 at 15:00
I have a gas mantle (or ten 
) and I see the same peak of 228Ac at 911keV in its
spectrum. BTW the 228Ac only occurs in the 232Th decay series, not from any other isotope of thorium from the other decay series. And yes, ThO2 and
UO2 have almost the same crystal parameters. It's still weird to see that much 228Ac in a uranium mineral... it's not just a trace.
violet sin - 30-9-2021 at 16:55
Th present I U ores depend on the ore type. I've been reading up about the subject after acquisition of several pounds of ore. Not to sound
pretentious or trying to correct anyone.
My understanding is, the difference is some U ores are primarily to exclusively, secondary minerals. U +6 is mobile, U+4/Th+4 aren't nearly so. If
it's got primary like pitchblende uranothorite etc. they can easily be present Th, or by definition required.
Of course there are mixed primary/secondary mineral deposits like many I have where the limestone is full of ribbons it bands of secondary issuing
from black grains in matrix. Again easily a mix of Th with U.
But if it's like some if the sandstone or sand that's glued together by uranium secondary minerals such as tyuyamunite, or when the U+6 gets
reduced by organic material, thorium can be left behind in the lower portion of the carbonate/sulfate lense, bedrock or wherever it was concentrated
from.
There was some old mining or geology notes I located for the area much of my samples were coming from. I forgot the details but the U was possibly
leached from granitic stone or pegmatite below. While water was leaving the region it concentrated. Much of my samples were from New Mexico by
Grant's. Hope the details are useful or at least not intrusive. I've no Gama spectrometer, so I can't comment in that regard. Wish I did 
sounds fun.
stamasd - 1-10-2021 at 02:27
Thank you, that is useful.
neptunium - 27-4-2024 at 06:50
If you are talking about Th232, this is a geology question. The way the 2 metals oxidation states brings them together throughout the earth`s history.
But, Thorium is also part of the decay chain of uranium, Th231 and Th227 for U235 and Th234 and Th230 from U238, (chemically speaking)
I don`t know what type of Gamma spectrometer you are using and how good the resolution is but Protactinium234m can also pop up in the vicinity of the
Ac228 peak. Just a thought...