I asked the Health Physics Society about radiation dangers concerning Autunite and safe exposure times. Their answer can be found below or click here to view it on their site. 

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Q. For the past few years I have been collecting and selling various minerals. Recently I have discovered a very large deposit of Autunite. I have a CDV 700 Geiger counter which peaks out with the probe up to 1 inch away from a specimen and the shield open. That's over 30,000 counts/minute. With the shield closed the readings are 2 to 5 mR/Hr. How dangerous is this amount of radioactivity? What would be safe exposure time to this mineral? Thanks, Ron

A. To answer this question, I must address a number of somewhat independent issues. The bottom line will be that you really have nothing to concern yourself about as long as you are not accumulating large quantities of the ore.

1. Measurements made with an old instrument that hasn't been calibrated will be of questionable accuracy. Even with a properly working instrument, measurements made close to a source (e.g., at one inch) can be misleading. This is because accurate readings require that the strength of the radiation field be uniform throughout the volume of the detector (the GM probe) and this will not be the case close to the source.
    

2. The portion of your body receiving the highest dose will be your hands and the hands are relatively insensitive to radiation. The portion of the body of most concern, the trunk, will receive a much lower dose because the intensity of radiation from a small source decreases dramatically with distance.
    

3. Even if your entire body received 2 mR/hr (which is impossible from such a sample) for eight hours a day, five days a week, and fifty weeks a year, your exposure would be less than the 5000 millirem annual limit which is considered "safe" by the regulatory community for radiation workers. There is no relevant limit that precisely fits your situation, but members of the public have sometimes been "limited" to 100 or 500 millirem per year.
    

4. I am unaware of any radiation injuries or other biological effects that have been attributed to the mere handling of radioactive ore. The increased risk of cancer observed in the underground uranium miners was due to the high levels of radon in the mines—not the direct radiation from the ore.
    

5. Having said all this, the guiding philosophy in the radiation safety community is that we should keep exposures to radiation as low as reasonably achievable. This is what we refer to as the ALARA principle.

The simple ways for you to achieve this would be to reduce the amount of time you handle the ore, keep the ore stored at some distance from occupied areas, and store the ore in a shielded container or room (e.g., a room with brick walls). These actions are really "overkill" for the small sample you have described however. Their main benefit might be to provide "peace of mind."

Paul Frame, CHP, Ph.D.

I also asked specifically about Alpha, Beta and Gamma from an Autunite specimen. Their answer is below or click here to view it on their site

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Q. Earlier I submitted Question #573 and was pleased with the answer. That question dealt with gamma radiation from mineral specimens I harvest. I now have a breakdown of the percent of alpha, beta, and gamma and would like to know, considering this new information, what my risks are. Our autunite produces 3% gamma, 62% beta, and 35% alpha. Our specimens will average 3 to 6 mR/hr gamma.

A.  As you may know, autunite is Ca(UO₂)₂(PO₄)₂-10H₂O, Hydrated Calcium Uranyl Phosphate, and poses and very minimal risk to you. The radiation from uranium is a very low external hazard. The dead layer of the skin stops the alphas that are emitted from this mineral. Only a small percentage of the betas emitted are energetic enough to get through the skin. With both the alphas and betas, one only needs to worry about the ones that are released from the material that is on the very outside of the sample; all others are shielded by the mineral itself. As a matter of fact, the gammas that are emitted are of very low energy as well and many of them do not get out of the sample either. As was mentioned, this sample is a very minimal external hazard and the only way that it would give you any appreciative dose would be if you ate it. And even then, given the dose rate that you gave (I assumed that the dose rate was on contact with the sample), the dose received would not be substantial enough to cause any harm. The thing that you have to worry about most is the degradation of your sample. I have read that over time autunite loses water and becomes meta-autunite. Many museums try very hard to maintain the integrity of their good autunite samples.

Kenneth Krieger

Autunite is a naturally occurring radioactive mineral. The amount of radiation produced by a specimen will vary depending on how much actual Autunite is on a specimen. Usually Autunite will be found as crystals deposited on the exterior of a rock which is usually Granite. The Autunite will be a very small amount compared to mass of the entire specimen. A specimen weighing one pound may only contain 1 or 2 grams of actual Autunite. 

Autunite produces mostly Alpha and Beta radiation and only a small amount of Gamma. Our specimens produce 35% Alpha, 62% Beta and 3% Gamma. Alpha and Beta radiation are stopped by almost any shielding. Paper, tin foil, and your skin will stop most of these types of radiation from entering your body. They are of little concern in regard to external exposure. 

Autunite is also a toxic metal when ingested. We developed a list of safety guidelines which should help the collector safely collect and store most radioactive mineral specimens. These guidelines are similar to safety guidelines for any toxic substance such as paint, oil or household chemicals. They may be viewed at:

  http://www.gothotrocks.com/website/pages/Safety.htm

We hope this page has answered your questions and concerns regarding Autunite. If you have any question not answered please email me.                     Ron@GotHotRocks.com