We purchased a pair of earrings over the Internet from the USA. They were to be given as a Christmas gift to a friend of the family. I decided to test them with a new computer based Geiger counter I had just assembled.
To my surprise these earrings turned out to be considerably radioactive. From the front side, and with the earrings next to each other, they tested 0.90 uSv/hr. Normal background here has been around 0.10 uSv/hr, so these earrings where testing 9 times background.
Originally thought the radioactivity was coming from the blue Topaz looking centre stones in this design, because there have been reports of radioactive Topaz being detected in jewelry. After removing these blue stones, and retesting the earrings, the light yellowy green stones positioned around these blue stones, were found to be the main source of the radioactivity.
Here are the scintillator and Geiger test charts results for the earrings test. The main isotopes detected were Thorium Th-234 and Uranium U-235.
The Thorium Th-234 is from Uranium U-238 decay. U-238 puts out hardly any gamma, but the Thorium Th-234 puts out enough for the scintillator equipment to detect it. The presence of Thorium indicates the presence of Uranium U-238, as Thorium Th-234 is a decay daughter of Uranium U-238.
Scintillator test Chart of earrings
This explains why there was so much beta detection with the Geiger test. Couldn't work out why at first. Thorium Th-234 puts out a lot of beta, and a small amount of gamma radiation.
Geiger Counter test chart using a Russian SBT-10 pancake tube. (Information on how to build your own computer based Geiger counter, for under $100, will be in next month magazine.)
Thorium Th-234 info
The small yellowy/green stones on the earrings are Uranium glass made from purified Uranium ore, because there are no decay daughters of Lead Pb-214 or Bismuth Bi-214 isotopes present. It would appear that someone is supplying Uranium glass stones to the jewelry industry.
Most of the radiation is beta radiation with a small gamma component. This is manly from the Thorium 234 decay. Most of the beta radiation body exposure is blocked by the glass stone metal mountings, in this particular earring jewelry design.
Using the Geiger Counter with the SBT-10 tube I detected approximately an extra 0.06 uSv/hr, above background from the rear of the earrings, as opposed to 0.90 uSv/hr from the front.
The Alpha output by Uranium U-238 and U-235 isotopes would be locked into the glass.
Do these earrings pose a health hazard? Probably not in this design, as the wearer is protected from most of the radiation by the metal mountings during use. A resent commenter pointed out that when beta radiation hits metal it can produce bremsstrahlung secondary radiation. This also maybe a potential hazard that needs further investigation.
Do the stones themselves pose a health hazard? Maybe in these, or some other unforeseen circumstances.
Listed in order of possible risk
A. At a manufacturer site or jewelry store, where these stones could be stored in bulk. Being exposed to the dust from cutting or polishing this type of glass, in these environments, could pose the greatest health risk.
B. People spending long hours close up to the jewelry during assembly.
C. A person who had collected a lot of this type of jewelry, and stored it close to where they sleep.
D. Different types of jewelry design using these stones, could be potentially hazardous in these circumstances
1. The piece used larger stones, or more stones.
2. Thinner metal mountings were used.
3. If a piece was worn close to the body. The more proximity and surface area touching the body, means more radiation exposure.
It is suggested that those of you with Geiger Counters, check everything that comes into your house.
Next month I will provide information on how to build, and set up, this computer based Geiger counter kit used for testing in this article. The open source Geiger counter software and USB hardware modules, plus Geiger tube, cost under $100.
Not only can these USB hardware modules be used to set up a cheap professional lab quality Geiger counter, they can also can be used to set up computer based motor control, light and temperature sensors, plus used to build computer based robotics very cheaply. The Geiger counter kit is probably the simplest item to build using these modules, and easiest project for members to build, to try their hand at this fascinating area of computer technology. For those members who are interested the hardware modules will be available for members to take home and experiment with.
Disclaimer: This is an amateur volunteer run service. Human error can provide incorrect information, and equipment malfunction can produce false readings. Do not rely on, or take action upon information presented on this web site, without further research. Views expressed in the pages or images on the SCCC Inc., site maybe the personal opinions of the relevant writers, and are not necessarily representative of those of SCCC Inc.