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Charoite radioactivity


#1

Hello Folks, I have a question. I went to a mineral show recently
seeking as to the purported radioactivity of heliodor
crystals. Walter Schumanns books state the pigment is uranium oxide
and that it is radioactive. Well before I use it in jewelry I wanted
to find out how radioactive it is. The person at the mineral booth had
a geiger counter and it did show higher than background radiation for
heliodor. The person owning the unit did not know the amounts that the
numbers refered to. She also said that charoite is hot too. She
performed the same test on the charoite that she did on the heliodor
and the numbers were up a little from the other reading and higher
than background. Again my concern is how much is too much. And how do
I determine what those numbers are. I dont have access to the unit
that was used, but again the numbers that were showing on the screen
didnt climb dramatically over what was present as background, but
without knowing what type of scale I was looking at, the numbers are
essentially meaningless. SO… I dont want to irradiate my customers.
And I have a fairly extensive collection of the utterly gorgeous
charoite. HELP!! How hot is this stuff??? , Heliodor too?? Any info
appreciated. Barney BeGuhl Joyful Crow Fine Metalworks Eugene Or.


#2

Barney, almost any rock, containing a large number of chemical
elements, will be hotter than background. As much as I know from the
original literature in Russian, no serious r-activity was reported for
charoite. There should also be no secondary r-activity, since the
stuff was not exposed overground when USSR conducted nuclear tests,
and is found rather far from the test sites.

Should like to warn about very spectacular agate, coming from
Kazakhstan, from the very hot region. I have (only) suspiction it may
be hot, so if you are offered this material do test it.

Eddie, chemist from Latvia


#3

Hi Barney, I don’t know about the minerals in question (I occasionally
work with radium in WWII instruments), but I can tell you about
radiation. The Australian OH&S standards allow for a worker to be
exposed to 20 milli sieverts (mSv) per year over five years. If you
do the maths, this works out to an exposure of 10 micro sieverts per
hour. You would want your mineral to radiate less that 10 micro Sv’s
per hour. Unfortunately, most Geiger counters measure in milli rads
per hour (mR/hr) and, as far as I know, these are not translatable
into sieverts. As a rule of thumb, less than 0.2 mR/hr is a good
safety margin. The amount of radiation absorbed by the body is also
affected by where the radiation occurs - breasts are 5 times more
susceptible to radiation than other areas of skin, your eyes are 15
times more susceptible than breasts. So you may want to take this
into account when designing your jewellery. Radiation comes in three
forms - alpha, beta and gamma particles. Alpha are more destructive
but do not travel very far (only cm’s). They are stopped easily.
Beta particles, often accompanied by gamma particles, travel further
(up to 7 meters depending on the radioactive isotope). They can also
be stopped but in doing so will generate gamma particles (x-rays). I
suppose this brings us to safety. Three things are possible: restrict
time exposed, increase the distance between you and the source and
shielding. Shielding against beta can be as little as sheet acrylic
and full skin coverage (latex gloves, long sleeved shirt, hair back,
glasses). With alpha particles, distance is best, but again shielding
is also effective. Gamma particles require the lead for really
effective shielding. I’m trying not to throw the text book at you (it
tends to hurt) but I hope that I’ve given you enough to
think about. If you have any more questions I’m happy to answer them