Vermiculite and asbestos
I just read several disturbing investigative articles in our local newspaper (Times of Trenton) about a now closed W.R. Grace Company vermiculite processing plant located in central New Jersey. Apparently the company was using tremolite asbestos contaminated mica to make the vermiculite by heating it to a high temperature until the mica would pop or puff up because the moisture contained in the mica would instantly turn to steam much like making pop corn. This vermiculite was named zonolite and used as attic insulation in as much as 30 million homes but also sold as a mixture in potting soils and bagged as garden vermiculite. The article dealt with the asbestos dust contamination of the surrounding neighborhood and the workers affected by breathing the choking dust that was so thick they could barely see much less breathe and their subsequent medical problems.
I don't know if this is why we see a dearth of vermiculite in stores but it is disturbing to think that many of us may have been unknowingly exposed to asbestos. Of course there must have been other companies producing and may be still producing uncontaminated vermiculite but according to the article the Libby mine (Libby, Montana) produced 75% of the world's ore contaminated with tremolite asbestos which the W.R. Grace Company used to produce the vermiculite.
Not a pleasant thing to contemplate.