Archived posting to the Leica Users Group, 1996/04/04
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Charles E. Dunlap wrote: > La has two naturally occuring isotopes: La-139 is stable and has a relative > abundance in nature of 99.91% while La-138 has a half life of 105 billion > years (>20 times the age of the Earth) and an abundance of 0.09%. La in > optical glass or even in pure elemental form would not be considered > radioactive in the lay use of the term. Interesting. Then what I was reading must have been info on the fact that LA type rare earth glasses were NOT radioactive. There was some sort of glass in those days that was stirring up a controversy because of the radioactivity of the elements. Of course, back in the 50s (right up 'til today) there was a lot of hysteria with anything radioactive. Even Ansel Adams (latest victim of Bill Gate's ever expanding empire) left the Sierra Club over the issue of atomic energy. -- Eric Welch Grants Pass, OR