Why do some radioactive elements emit a green glow?

[SUDOnym]

Hello

I am doing radioactivity with my year 10 class and it has set me think about something.
I would be grateful for clarification on the following issue and also any other facts that you would like to share that would be of interest to 14 year olds!

My issue: all the famous radioactive elements (eg. uranium, plutonium, polonium) look just like any other metal (ie. silver). In what instance will we get the famous "green glow"?
That glow is not a myth is it? - for example I have heard a number of times that before they were aware of the danger of radioactive elements women used to wear glowing green jewellery! (Please don't tell me that's not true!).
My thinking: One possible explanation I can think of for a green glow would be that the ionising radiation from the radioactive source would excite / ionise oxygen atoms and so when the atoms de-excite they emit green light (just like what happens with aurora... OIII is the emission line there?).

Thanks

 

[Bill_K]

SUDOnym, Green or blue? You may be referring to the blue Cherenkov radiation that's seen in the water surrounding nuclear reactors.

 

[SUDOnym]

definitely green... skip to 7:00 minutes of the following link. http://www.youtube.com/watch?v=h4XIOpKWc1Y

However, a browse around wikipedia leads me to think that it is probably radium I am thinking of...

 

[Astronuc]

There are various fluorescent minerals which glow under UV, and in theory they would glow in the presence of beta/gamma radiation.
http://geoinfo.nmt.edu/publications/circulars/downloads/15/Circular%2015.pdf