Using Coal Slag as a Substrate

["Rod Reeves" <reeves_rod at hotmail_com>]

Has anyone used coal slag (sandblasting grade) as a substrate?  It appears
to be more coarse than silica sand and according to the manufacturer has a
neutral pH.  I like the color and was wanting to use it in combination with
laterite in a planted aquarium.  I know that Seachem's flourite is highly
rated but am searching for a lower cost alternative.