Radon Halo Formation In A Nutshell
Uranium 238 bearing mineral particles exist in mica, which is cracked, split, and weakly bonded between crystal planes.
These cracks have wide and narrow spots, twists, turns, and bends. They can interrupt and delay atoms' travels in them.
U-238 atoms decay, through eight alpha-particle-emitting steps (and a few beta-emitting). The fifth is Radon 222.
Radon is a "noble" gas. It sticks to nothing. Radon atoms wander into the cracks and into the mica 'leaves', driven by thermal
shaking and by additional gas atoms released behind them.
Once in there, on average in four days, they decay and stop moving, producing in turn the three Poloniums, 218, 214, and 210,
and marking the mica (var. biotite) with those wonderful little bullseye rings.
The deposition process along the crack is complex. For example, polonium's end decay product, Lead, gathers in the crack,
narrowing it even further, which affects subsequent Radon atoms' paths down the crack.
The halo formation process takes a very, very long time indeed. It does not happen in weeks, years, decades, or even milllennia.
Many hundreds of millions of individual decays must take place before an halo becomes visible to the eye.
Notice the effect of this elegant and complicated process, graphically displayed in the above photomicrograph.
NOTE to ALL: Science demands rigor, and no photograph of any quality (let alone these web-accessible digiphotos)
can possibly substitute for the naked eye pressed to a good microscope's eyepiece. IF you are seriously concerned
or interested in this "controversy," it behooves you to get your own samples and your own microscope
(borrow one), and do this examination for your very own self !
(Especially if your faith depends upon getting the truth right the first time!)
--John Brawley August, 2005