(youtube) A thorite mineral containing Thorium 232 which produce Thoron (220Rn) trough the decay of 224Ra.
Thoron is in gaseous form and is floating in the chamber. It has a period of 55 second, then decay with an alpha to 216Po, which have a half life of 0.145 second and decay to 212 Pb with the emission of an other alpha.
In the video with the thorite ore you may see some L or V shape, it is the simultaneous decay of thoron and polonium. At the beginning, thoron decay to one point in the chamber, making polonium and an alpha. The polonium nucleus unstable, disintegrate immediately once created into lead and emit an alpha which go in various direction : we see a L or V shape of ionisation. The lead 212 has a too long half live (10.6h) to see the electron emitted .
This incredible mineral produce a lot of thoron for it's size. It come fromhttp://minresco.com/
where you can find some quality radioactive mineral, and trinitite.