On 6/5/2013 6:58 AM, Jim Elbrecht wrote:
"HeyBub" wrote:
-snip-

The disadvantage is the cost. For example, Vermiculite costs $35+ for 4
cubic feet. A ten by four bed would need 6+ cubic feet.


Holy crap-- I'll have to be more careful with my 30gallon bin of that
stuff. I don't think I paid $10 for it maybe 5-10yrs ago. I bought
a couple bags from an insulation place. I wonder what made it
go up so.

Google 'vermiculite asbestos' and you'll see why. Basically, the
world's largest vermiculite mine (located in Montana) produced
vermiculite contaminated with asbestos. Most vermiculite sold in the
US up till 1990 came from that mine, and is most likely contaminated.
That mine is now closed and vermiculite mined from other locations is
tested to ensure that it does not contain asbestos. It's also why the
majority of potting/soil mixtures sold in the US no longer contain
much, if any, vermiculite. Between its reputation and expense, it's a
non-starter.