has been "popped" with heat. It is inert, and
holds water like a sponge. It is often mixed
with other ingredients to loosen the mix and
aid in both its water and air retention. It
comes in various sizes. The coarse and
medium sizes are preferred because they
allow more air to form between the particles
than the fine. Vermiculite is very light
weight
CAUTION: Dry vermiculite produces
a lot of dust which is
harmful to breathe. It
contains minute amounts
of asbestos. Before using
the material wet it down
with water. This prevents
the dust from forming. It
comes in 4 cubic foot
bags at nurseries and
grow stores.PERLITE - is puffed volcanic pumice. It
does not absorb water, but holds it on/in its
pitted surface. It is used to loosen planting
mixes and stabilize their water holding
properties. It is so light weight it floats in
water. It comes in various sizes. Coarse
perlite allows the most air to mix with the
medium.