I have a box of Ironite that I'm trying to figure out how to get rid of.
I believe it has been banned for sale here in Minnesota for several
years, but I bought it about 5 years ago before I knew what it was.
There is no mention on the box about the heavy metals content.

The stuff is ground up mine tailings from a toxic waste site in Arizona.
The arsenic and lead is probably bound up and not bioavailable, but if
so, the iron is also bound up and not available. It's not worth taking
a chance and contaminating ones soil with toxic heavy metals.

For that hydrangea or azalea, just use copperas (ferrous sulfate,) or
sulfur, or a little aluminum sulfate as an acidifier. At least you know
what's in them.

Best regards,
Bob