I'm sure someone will have a more competent answer, but
my understanding is that perlite is very similar to pumice,
i.e. it's heat expanded rock. Vermiculite is heat expanded
mica (aka. accordion rock :-)). Rick has told me that the
latter is slightly alkaline, but I think perlite is completely
neutral. For the newbies out there, one adds perlite to a mix
to "lighten it", or give it better drainage, while vermiculite
does the opposite, and allows a mix to hold water better (in the
little accordian folds).
Both components come in different granularities. I like using
the finger grade vermiculite, which is a bit harder to find,
since typically everyone carrys the Rod McClelland medium size.
The fine stuff is much better for small CP, and a spoon of it
wet looks similar to black & mica fine beach sand (like the stuff
at the waters edge).
>>soil mixes, but what is it? For that matter, I'm not entirely sure what
>>vermiculite. For my rock-collecting youth, I seem to recall it is some
>>kind of rock like mica that has been expanded via heat...BUT what is
>>perlite? Has anyone with a bent to CP done any chemistry tests on it?
>>Is it acidic? I use it for my Mexican pings and Heliamphora, but not
>>much else.
I use perlite w/ peat for all North American CP (sometimes with
a top dressing of peat or live spaghnum to make it look nice.
I also use perlite w/ sand and peat for drosophyllum. I use vermic.
& perlite for mexican pings. Peat/sand for tuberous drosera, and
for pygmies. Live spaghnum for a few very special plants like
Heliamphora. Peat/perlite/fine-orchid-bark for Nepenthes.
R.