Tom, As far as I could make out from webelements dot com, none of the two naturally occurring isotopes are radioactive. http://www.webelements.com/webelements/elements/text/La/key.html
There are a couple of lanthanides that are, though. Most notably Thorium, of course... Jostein ----- Original Message ----- From: "graywolf" <[EMAIL PROTECTED]> > > Isn't lanthanum slightly radioactive too? > > -- > > Jeff Jonsson wrote: > > So does anyone have any of these lenses made with radioactive Thorium? > > > > http://www.orau.org/ptp/collection/consumer%20products/cameralens.htm > >
