Uranium is radioactive but the emissions are alpha particles, which will not penetrate the skin. Uranium spontaneously decays into a long list of "daughter" elements, some of which emit beta particles. Beta particles will penetrate into the skin about 2 mm (0.08") depth, so your internal organs are not at risk. So despite it's "public image", uranium is considered to be a weak external radiation hazard.

The main hazard from uranium is actually not from the particles emitted. Uranium is very toxic and ingesting it or inhaling the dust creates two bigger problems - the emitted alpha and beta particles, once inside the body, can do localized damage. It is a heavy metal and by itself is toxic in a similar manner as lead. So do not eat your beads, or grind them and inhale the dust, etc. Since glass dust in general has other toxic components, the same precautions would hold for UG beads as well, if not more. Even with these cautions, it was not considered a problem to eat or drink from UG glassware, despite the fact that tiny amounts of UG would enter your system.

Nice summaries of the hazards of particle emissions:

Alpha: https://emilms.fema.gov/IS3/FEMA_IS/is03/REM0202130.htm

Beta: https://emilms.fema.gov/IS3/FEMA_IS/is03/REM0202140.htm

My Geiger counter (GC) has a built-in check so I know it is functioning normally, although it has not been officially calibrated. The GC detects beta and gamma rays. I haven;t said anything about gamma rays but I determined that the beads did not emit any, which is in accordance with the fact that uranium nor any of the daughter elements emit gamma rays.

I received the 5 beads from Audrey that are shown in the picture. The top 3 are more blue-green and the bottom are more yellow-green. The beads had slightly different weights so I "normalized" the readings for each bead to 2.5g. As you can see, the green beads had somewhat higher readings than the blue beads, so they likely had more of the uranium salt that produces the green-yellow color.

I could not get the beads to physically touch the detector tube, which is guarded by a protective film and a metal grate. The beads were about 0.10" from the detector tube. So the readings right at your skin surface would be a bit higher.

For reference, during the time I was doing these tests, the background readings were around 0.01 mrem/hr. This value was subtracted from the readings to give just the amount due to the beads.

The readings are listed as mrem/hr (milli rem per hour, also written as mR/hr). Now for some calculations:

The average reading was 0.041 mrem/hr. If a necklace had 30 beads of 2.5g, the dose would be 0.041 x 30 = 1.23 mrem/hr from the necklace. If you use more or less beads you can calculate a new value accordingly.

To make sense of this number, first note that radiation safety is generally described in terms of total rems exposure per year. Natural exposure from inhaling air, drinking water, eating food, and radiation from cosmic rays and from the earth amounts to 300 mrem in a year. Additional radiation comes from things like a mammogram (40 -42 mrem), a chest xray (6-10 mrem) or airplane flights (cross-country gets you 3.5 mrem). CT and CT/PET scans run pretty high - 1000 mrem and 2500 mrem respectively. For another data point, a worker in a radiation business has a limit of 5000 mrem per year, with a total of 10,000 mrem over 5 years. Note that these figures don't depend on what type of radiation it is - alpha, beta, gamma, xray, are all treated as radiation exposure.

So to get a dose equal to a mammogram, you would have to wear your beads for 40/1.23 = 32.5 hours.

Here's what I did for my own beads that I found had UG - I put a note under the 5 necklaces with a reminder to limit wearing to 40 hours per year, since I don't have a lot of larger beads on these strands.

The 40 hours is super conservative. Unless you happen to have a year where you get a number of CT scans and dozens of airplane flights, I wouldn't worry about wearing the beads for several hundred hours or more. Or if you have skin cancer or some other skin condition on your chest and neck, I'd be extra cautious.

So in summary, check your beads for UG with a black light. Then use some common sense with regards to number of hours wearing them, and don't eat or grind them.

Note - there are reports of UG glassware with very high uranium content - up to 25% instead of a more typical 2%. I have no idea if there are beads made with the higher content. But you can see from the calculations, that even if your beads have ten times the uranium content, limiting your wear to a sensible duration every year will still put you below something like a CT scan in exposure. And the exposure is only to your skin, not internally like the CT scan.

Hope this helps!

Forget to mention that the emission drops off very quickly with distance. At about 12" away from the beads, there is no reading above background. So don't worry about being in the same room with your beads all day long.