Apatite - Radioactive??

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Richard Hull
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Apatite - Radioactive??

Post by Richard Hull »

About a year ago I went to a mineral show with my GM counter. The only mildly radioactive mineral that I found was apatite. Apatite is a phosphate mineral and contains no radioactive element in its given chemical formula. I thought little of it then as the level was on the order of 200-300 cpm which is about 4-6 times the background level when using my Geiger counter. Some granitic driveway stone might measure this much. Of course, we all know granite is commonly known to be in this range, harboring hidden uranium.

Apatite, if investigated in the literature, is not considered radioactive. Lauf's extensive book on the thorium and uranium minerals doesn't mention apatite. This, I attribute to apatite not being a common ore of either of these elements.

I went to another mineral show over the weekend with my GM counter and found several samples of apatite from 4 different dealers all were radioactive. I purchased samples of apatite from each dealer. I asked where the dealers obtained their apatite from. I found that they claimed either Brazil, Madagascar, or Myanmar (old Burma). These are not the only places apatite is found, but oddly all these places are known to contain monazites. Monazites are known to contain both uranium and thorium with thorium to be the most often found constituent to as much as 50% thorium in some monazites.

I placed my purchased apatite on my gamma ray spectrometer and found only a Thorium signature. The assumption here is that over the period of formation of apatite, some tramp thorium was included in its matrix due to the various location's propensity to monazitic thorium.

I attach images of my apatite samples which were grouped around my 3X3 sodium iodide PMT detector. I also attach a screen shot of a mere 720 second live time spectrographic detection period with a bold and clear indication of only thorium being present with no hint of uranium. It is nice knowing that apatite, no matter where collected from the common sources of the mineral on earth, will be most likely to harbor thorium as a part of its makeup. Both uranium and thorium are known to chemically attach to phosphates with ease as weathered products. Unsuspected and unheralded in most books and scholarly expositions on this mineral, Thorium is a common constituent. The polished raw stones cut from this soft material appear as varying shades of blue or green.

Richard Hull
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Polished stones of apatite from bluish to dark green collected from at least three widely separated parts of the planet, all known for monazite deposits containing thorium.
Polished stones of apatite from bluish to dark green collected from at least three widely separated parts of the planet, all known for monazite deposits containing thorium.
My gamma spectrometer shows that only thorium is present in these samples of apatite after an unusually short live time of about 720 seconds.  The GM counter typically only detects surface betas for the most part and very few gammas.  The gamma spectrometer shows a very large gamma detection signal. This indicates a rather large presence of thorium in this apatite that the GM counter barely detects.
My gamma spectrometer shows that only thorium is present in these samples of apatite after an unusually short live time of about 720 seconds. The GM counter typically only detects surface betas for the most part and very few gammas. The gamma spectrometer shows a very large gamma detection signal. This indicates a rather large presence of thorium in this apatite that the GM counter barely detects.
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Apatite - Radioactive??

Post by Dennis P Brown »

Nice detective work, Richard.
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Re: Apatite - Radioactive??

Post by John Futter »

Richard
here in New zealand we have a few problems with fertilser. Many farms are now not allowed to put on more phosphate fertiliser.
The two main problems are cadmium and uranium buildup in the soils due to phosphate fertilisers especially from northern Africa
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Jim Kovalchick
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Re: Apatite - Radioactive??

Post by Jim Kovalchick »

Richard,
There is a USGS report that acknowledges that trace amounts of uranium are ubiquitous to apatite. This paper is an in depth study. You might also find the discussion of thorium and monazite in the paper interesting.

By the way, this report addresses uranium content within phosphate nodules in the Charleston, South Carolina phosphate area. I routinely find radioactive nodules on the beach near my home in Myrtle Beach. The nodule count rate on a two inch pancake ranges from almost undetectable to several times background for the smooth and dark nodules and up to 2000 cpm for the weathered, lighter colored ones. The nodules are mostly carbonate-fluorapatite.

Jim

https://pubs.usgs.gov/pp/0314d/report.pdf
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Jim Kovalchick
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Re: Apatite - Radioactive??

Post by Jim Kovalchick »

This is a raw nodule sample from the surf edge in Myrtle Beach, South Carolina. It is carbonate-fluorapatite, and nearly 2000 cpm on a pancake.
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Re: Apatite - Radioactive??

Post by Richard Hull »

Thanks Jim for the paper PDF.
Phosphates combine in weathered Uranium. To make urano-phosphate compounds. very common.
Cool nodule image.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Apatite - Radioactive??

Post by Dennis P Brown »

So in Myrtle Beach, one can be tanned from more than just UV radiation ;)
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Richard Hull
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Re: Apatite - Radioactive??

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I checked my apatite pieces with a 2-inch pancake probe.

Large piece 2800 cpm.
all the remaining pieces 1800-2100 cpm.

For searching at mineral shows, I take a special counter that is mica windowed which I made up myself for this purpose. Back in 2020 at the big HEAS flea market here, I purchase a bunch of 7616 GM tubes. Oddly, these are tiny mica windowed tubes. (1/4-inch diameter window!) They were, for some unknown reason, used inside later PDR-27 High end government GM counters. Buried deep inside the thick walled, heavy, aluminum case, they were used in place of the common 5980 gamma only tube used in the PDR series for years. This meant the small mica window was useless! No alpha or beta radiation could enter the case! The steel shell of the tube relied on gamma detection via photo electric and Compton scattering to produce electrons into the tiny tube's volume just as in the old 5980 tubes. A true puzzle for me as to why? The best I can figure is the 7616 has 3 times the volume over the old 5980 making it a bit more gamma sensitive.

Note: The PDR-27 had a special high range where the normal hand held probe, 1-inch mica windowed alpha, beta, gamma tube is shut down and only the internal, gamma only 5980 tube is used to read very hot, high gamma fields free of any local beta particle emitters.

The beauty of these little 7617 tubes make excellent spot check GM tubes for alpha, beta, gamma detection. They require a minimum of about 700 volts to function. They are the sweetest little tubes I have ever seen, and are great for searching for blebs of U and Th on a mineral specimen. However, they are not good for general detection due to the very small mica window compared to the huge 2" pancake on the finest of GM counters.

From the above cpm values on the pancake probe, the little tube shows no more than about 300 cpm. Of course the background is only about 5 cpm so it still sounds off nicely on a "strike" of a radioactive mineral.

I attach some images of this little guy. LND still has it in their catalog!

Richard Hull
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My cute little "show" GM counter with 4 line Oled display
My cute little "show" GM counter with 4 line Oled display
Here is that little counter opened for "guts" inspection with the little 7616 tube's mica window looking through a 3/8 diameter hole in the case.  I use a special smaller GM Arduino pro-mini board that only drives I2C displays.
Here is that little counter opened for "guts" inspection with the little 7616 tube's mica window looking through a 3/8 diameter hole in the case. I use a special smaller GM Arduino pro-mini board that only drives I2C displays.
Nifty little mica windowed tube used in my tiny GM <br />counter used to detect radioactive minerals at shows.
Nifty little mica windowed tube used in my tiny GM
counter used to detect radioactive minerals at shows.
Spec sheet for the above 7617 tube shows that this mica windowed tube with more volume will detect gamma with 10 counts/sec = 1mrem. three times what the 5980 below will detect.  Plus, with the mica window, if outside, will detect alpha, beta and gamma.
Spec sheet for the above 7617 tube shows that this mica windowed tube with more volume will detect gamma with 10 counts/sec = 1mrem. three times what the 5980 below will detect. Plus, with the mica window, if outside, will detect alpha, beta and gamma.
Totally sealed in steel shell no window.  Common gamma only tube used in most PDR series counters.
Totally sealed in steel shell no window. Common gamma only tube used in most PDR series counters.
Only 3 counts/sec will equal 1 mrem (gamma)
Only 3 counts/sec will equal 1 mrem (gamma)
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Jim Kovalchick
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Re: Apatite - Radioactive??

Post by Jim Kovalchick »

Richard,
I passed by a rock shop in North Georgia today, and I couldn't help asking them if they had any apatite. They had some polished green blue apatite that were cheap enough to bring home a couple for experiments. They were real hot, just 500 com on a pancake, but my RIID said they contain thorium.

Jim Kovalchick
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Richard Hull
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Re: Apatite - Radioactive??

Post by Richard Hull »

Interesting. They only seem to harbor Thorium. I have never heard of any U content. As I have said, they are found in monazite regions and monazite is the richest of all Thorium minerals. I paid $20.00 for my big piece in the image above. The small pieces were in the 8-12 dollar range. It is pretty, not rare at all and is just too soft to be of much use in jewelry. I did see a lot of bead strings of Apatite at the mineral/gem show. Wearing a large thorium laced bead necklace seems interesting. It is not dangerous, of course, unless you wear it every day for days on end. Thorium is famous for the 2.6 MEV gamma from one of its daughters.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Apatite - Radioactive??

Post by Jim Kovalchick »

Meant to say not very hot
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Richard Hull
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Re: Apatite - Radioactive??

Post by Richard Hull »

I crammed a gun show (morning) and a gem and mineral show (afternoon) into last Saturday. I found some naturally mined Apatite which I, personally, find far more interesting to the eye than those polished lumps shown in my original post, and the they cost far less with the same thorium content. The huge lumps I show here were $4.00 each and the smaller ones were $2.00 each. All were from Madagascar. Image below...

I also picked up 4 large Whale bone fossils found in Virginia for $10 for all. They are radioactive and my Gamma spec, Canberra 40, in only 500 seconds, gave a vivid uranium signature with "papa bear" showing over 3000 counts in just 500 seconds. Images below....

I have a good collection of fossilized whale bone and all are 100% tramp contained Uranium only.

Richard Hull
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Apatite -mined.anno.jpg
whalebone fossils.anno.jpg
whalebone gamma.anno.jpg
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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