Radioactivity and radioactive minerals
Many people practically paralyze when they hear the word 'radioactivity,' and though
highly radioactive substances should be treated with caution, nothing is gained from fear
and ignorance. This is written to explain radioactivity, if you are unfamiliar with it, to
allay fears, to avoid stupid mistakes when collecting radioactive minerals, and indeed by
somebody who has a dedicated personal interest in collecting radioactive minerals.
Discovery
The term 'radioactivity' originates from the Latin term 'radius', meaning 'rod' or 'ray'
and 'activity' - something goes on at a distance, following 'rays' from an object.
Radioactivity was discovered in 1896 by the French physicist and professor at Ecole
Polytechnique in Paris, Antoine Henri Becquerel (1852-1908) [for whom the secondary
uranium mineral Becquerelite is named], who shared the Nobel Award in 1903 with
Pierre and Marie Curie for the discovery. The earliest observations were on
photographic film that had been exposed (coloured) in a pattern, following rays from
substances containing uranium. They caused an activity (colouring the film) at a
distance, following rays from the source.
In 1899 the New Zealander Ernest Rutherford (1871-1937) [for whom the
secondary uranium mineral Rutherfordine is named] discovered that the radiation from
uranium had two components, a less penetrating 'alpha' radiation and a more penetrating
'beta' radiation, and shortly after Villard discovered the even more penetrating 'gamma'
radiation. Finally in 1902 Rutherford and the British physicist Frederick Soddy (1877-
1956) described radioactivity as the breaking up of an atom into a lighter one and
charged particles (alpha and beta radiation) with the release of energy as gamma
radiation.
Penetration revisited
Alpha and beta radiation is indeed less 'penetrating' than gamma, but let us just evaluate
that, because 'less penetrating' does not necessarily imply less harmful in a worst case
scenario. Alpha and beta radiation are both particles (equivalent to helium nuclei and
electrons, respectively, but that is not important in this context), and gamma radiation is
composed of 'electromagnetic waves' or 'photons' - physically the same as light, X-rays,
radio waves, etc., but far with more energy than the others. The particles' energy can be
absorbed piecemeal, that is they bump into a number of (many!) atoms, and set off some
energy in each. The gamma photons are either absorbed or not, that is, they give off all
their energy at once if absorbed. That leads to relevant qualitative differences - particle
radiation always has a limited range, depending on the material it is absorbed in, but
gamma radiation can theoretically reach 'infinitely' far. The particle radiation usually
carries less energy per unit than gamma radiation, but it will deposit that energy evenly
over a much smaller range. Basically alpha radiation is harmless, it is easily absorbed by
a sheet of paper or the upper (dead) cells of your skin - it will never reach live tissue.
But if you inhale a grain of material with high alpha activity, it may lodge on or
between live cells in the lungs and cause damage. Most gamma radiation, however, easily
passes through a hand, causing no damage - it was not absorbed, hence no damage. Some
obviously is absorbed, even if only a small proportion, and very strong gamma sources
indeed may cause serious injury. You may be familiar with stories from chiefly
developing countries (last time I believe was Thailand in the late 1990s), where poor
people scavenge and recycle garbage, get hold of strong cobalt-60 sources used to 'X-
ray' buildings, and injure themselves seriously.
Ubiquitous radioactivity
Essentially radioactivity is everywhere. You can not find any place on Earth without
measurable radioactivity and no, it is not because of nuclear bombs, the Sellafield plant
or any other human intervention. The sun's radiation constantly produces radioactive
carbon-14, that is incorporated into plants, eaten by other organisms, and incorporated
into their bodies. That is, we do contain radioactive substances ourselves. Most rocks
contain radioactive material, sometimes very little, sometimes quite a lot (like uranium
ore). On top of this comes radiation from outer space and obviously a contribution from
man-made sources. All of this is generally referred to as 'background radiation' - it may
be relatively higher or lower at given locations, but there is always some. That is,
radioactivity is a part of our lives, whether we like it or not.
ALARA and minerals
Radioactivity received considerable attention during the 20th Century, and few things we
can be exposed to are as well examined and quantified as radioactivity. Indeed serious
bodily injury may arise from radiation alone, and most countries have strict rules for
radiation exposure. There is no known minimum radiation level, that is known to be
safe, and most procedures apply the ALARA (As Low As Reasonably Achievable)
principle. That is, you try to shield persons and the environment against radiation, but
you always weigh the yield of an effort against the achievable result. It is always possible
to reduce radiation exposure but ultimately you reduce exposure very little even by a
huge effort - ALARA tells you to stop, before it gets crazy!
So where does that leave us with minerals? I can not give you any number, saying
'if you are below that, you are safe.' Technically a piece of feldspar is radioactive (albeit
very little) and so is a piece of Uraninite (considerably more). You can argue, that
ALARA tells you to get rid of the Uraninite, but keep the feldspar. That's fine, if that is
how you feel, but what you are doing is either implementing an arbitrary value between
'feldspar' and 'Uraninite' as safe - and absolutely no data support that - or you interpret
the 'R' in ALARA far more rigidly than I. That is OK - I disagree, but that is your
choice - but please do not pretend it is 'safe' or in any way qualified or substantiated by
data.
To put things in perspective, let me share with you that I have met a few
individuals, who were adamant that we 'need radiation to survive' and who would have
pieces of radioactive minerals in their home to 'feel better' (no, I am not making this
up). This too is unsubstantiated by data and I will allow myself some deep skepticism.
The radioactive water from the mines in Jachymov (Joachimsthal) in the Czech Republic
has a considerable following for therapeutic use. Personally I doubt the radioactivity has
any effect at all, though relaxing in a hot tub in the Bohemian mountains, enjoying the
local beer and food will be most therapeutic.
Personal approach
The best I can do is to tell you, how I collect, store and treat radioactive minerals, and
why. Note, no data documents this is safe just as well as none documents it is unsafe. I
like radioactive minerals, because they often have an interesting chemistry, they are
beautiful, and are part of 'the whole picture' when you collect minerals. Some specimens
are indeed 'very radioactive' (they make your Geiger counter buzz), but did you ever
notice what distance does? Moving the Geiger counter away from a specimen decreases
the buzz considerably - that is the effect per unit area goes down. The point I am trying
to make is, we only spend very little time in close proximity to the 'very radioactive'
specimens, and even they are often less radioactive than material that can be handled
safely without special precautions in a work environment. I tend to be quite laid back
with respect to that.
I do, however, always wash my hands after handling very radioactive minerals
(well, I usually wash my hands after handling minerals in general) - they are beautiful
and interesting, but I really don't want to breathe or eat their dust.
My radioactive minerals are stored with the rest. They are not kept behind lead,
stored in sealed containers or wrapped in plastic bags. Personally, I consider the direct
radiation produced by the specimens to be a negligible hazard, particularly as I am
hardly ever close enough to the specimens to get an appreciable exposure. Sealed
containers and plastic bags create more of a hazard, if anything. They may seal in radon
(a radioactive gas formed by the decomposition of uranium), and you will thus get a
small whiff of radioactive gas straight in your face, when you look at the specimens
every second year. I still believe it is negligible, but it is just silly.
The Torbernite killed him!
Yes, I do know of this or that collector who stored all his radioactive minerals under the
bed, lost all his hair and died from cancer. It is ... shall we say anecdotal? I do not say it
is not true, but do claim there is no connection. Storing your radioactive minerals under
your bed is dumb - not necessarily harmful, but just dumb. If there is any effect at all,
you will be exposed to it about eight hours every day. Keep your radioactive minerals -
and other minerals too! - in a cabinet in a proper place, not under the bed. Losing your
hair because of radiation is possible, but it is always caused by 'high' doses over short
time, not 'low' doses over long time - cancer patients often loose hair due to radiation
treatment, but they get high doses for a short time. Oh yes, cancer can be induced by
radiation, by all means, but sort of generic cancer is one of the leading causes of death in
the industrialized world, and seems to remain so whether or not you sleep on top of
your minerals. The basic information is probably correct, but the implied mechanism
most likely not.
Which?
Many collectors own a basic Geiger-Müller (GM) counter to 'identify radioactive
minerals.' By all means buy one, if you find it helpful, but do be aware of its limitations.
As mentioned above, radioactivity is ubiquitous, so you are only able to distinguish
'more' or 'less' radioactive. Most GM counters say 'click' when they register radiation
(some have a numerical scale as well), and allow you to distinguish 'appreciably' (f.ex.
Uraninite) and 'not appreciably' (f.ex. feldspar) radioactive minerals, but it is still up to
you to interpret the clicks. Are they 'negligible' or 'substantial'?
GM counters measure the amount of radiation, but do not identify anything. You
can not identify the mineral or chemical element causing the radiation, merely the
amount of radiation. This can be useful in field-trips, though. If you search 'radioactive'
minerals (f.ex. Uraninite crystals) in an essentially 'non-radioactive' host rock (f.ex.
pegmatite), a GM counter may be helpful locating collectible specimens. The draw-back
is, the GM counter only covers a small area - you may need to put it close to the ground
to get a signal, and it can be faster to search visually than with a GM counter.
Metamict
Most appreciably radioactive minerals contain either uranium (U) or thorium (Th) in
their chemical formula, and are easily identified in a book. A number of so-called Rare
Earth Element (REE) minerals and f.ex. Columbite/Tantalite may, however, contain
some uranium or thorium and be appreciably radioactive, even if neither is an essential
constituent of the formula. Many such minerals are 'metamict' - that means, the
radiation has destroyed the crystal lattice, and they are more or less glass-like. The
colour is often brown to black, the luster between sub-metallic and glassy, and you often
see an 'alteration zone' around the grains in their host rock. The alteration zone can be
anything from a thin, brownish band to a wide zone of brightly coloured, secondary
minerals.
Minerals that often contain appreciable uranium or thorium, even if it is not an
essential constituent, include Allanite, €schynite, Betafite, Columbite, Euxenite,
Polycrase, and Tantalite. Note, that specimens of these may have appreciable
radioactivity, but may also have no appreciable activity at all.
Specimen Handling
It is a fact, high doses of radioactive radiation may seriously harm your health. It is also
a fact, that no data documents the relatively low doses of radiation you are likely to
receive from specimens will in any way affect your health. It is also a fact, that even
very low doses of radiation may affect your health, even if we can not document it
except by the inherently unsound para-scientific approach of extrapolation. Sorry, but
we do not have any data whatsoever to substantiate a recommendation. Neither does
anybody else, though they may pretend otherwise.
Our view is, admittedly, based on faith only. That faith tells us, the potential
health hazard of collecting, storing, and handling radioactive mineral specimens is
equivalent to the potential health hazard of putting salt on your egg if you are a sporty,
healthy, 22-year old Caucasian male - ultimately, the egg may do more harm than the
salt.
Stay away from shielding and wrapping - ultimately it may do ore harm than
good, if there proves to be any health concerns at all.
If you feel uncertain or worried, don't collect radioactive minerals - there is
really no point in collecting items, that make you insecure. We gladly accept any
specimen, accompanied by appropriate locality data, as a donation. Want to get rid of
your Cornish Torbernite, go ahead and mail it. Unhappy about those Uraninite crystals?
We would REALLY like to get them! We believe radioactive minerals are fascinating
testimonies of our planet and the processes operating on it.
Bibliography
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This page is authored by Claus Hedegaard.
Mineraler