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Family's Fluorescent Rocks Page 14:
Radioactive Fluorescent Minerals
Thorite, AndersoniteMost fluorescent minerals are not radioactive, but some uranium and thorium containing minerals are both slightly radioactive and fluorescent.
See 3D Stereo pictures of radioactive minerals
(Click picture to enlarge)
Thorite ( above ) contains the radioactive elements thorium and uranium which each eject alpha particles, not beta, at the first step of each of their decay series. But thorium becomes radium 228 ( at the rate of half in 1.4E10 years ) and the radium 228 ( half-life 5.75 years) emits beta particles. Three of the remaining steps of the series, all with short half-lives, also produce beta. Uranium similarly has a very long half-life but the next two decays in its series are quick and both produce beta.
Beta particles are high speed electrons formed when neutrons decay. They can be stopped by thin plastic shielding.
On this page the Geiger counter was positioned for detecting beta particles in addition to gamma radiation. The detector is calibrated only for gamma but the presence of beta is determined by an increase in the counts when the slotted side of the instrument is aimed at the mineral or other radioactive source. When the Geiger counter is aimed straight at the sample the plastic case blocks the beta particles from reaching the detector tube but there are slots on one side to allow beta detection.
This 10 second sample ( above ) of clicks recorded from the Geiger counter with the beta slots facing the thorite at about one inch shows around 127 counts / 10 sec. or 762 counts / minute.
Andersonite (above ) Na2CaUO2(CO3)3-6H2O, is a minor ore of uranium. This sample is about 1-1/2" but the andersonite is just a thin coating as can be seen under UV.
This 10 second sample ( above ) of clicks recorded from the Geiger counter with the beta slots facing the andersonite at about one inch shows around 15 counts / 10 sec. or 90 counts / minute.
James E. Tozour, email@example.com
Last Updated 10/9/2015