On 05/12/2013 16:48, Fredxxx wrote:
....
Rather worrying comment at the end of the wiki article I hadn't heard
before concerning asbestos!

The concern is about vermiculite from the Libby Mine in Montana, which
also had a deposit of tremolite asbestos. About 70% of the vermiculite
sold in the USA from 1919 to 1990 was supplied from that mine, mainly
under the trade name Zonolite. Vermiculite supplied since 1990 is
considered to be safe, as is any that did not come from the Libby mine
before that.

Colin Bignell