On 05/12/2013 16:48, Fredxxx wrote: ...
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