Chrono,
Perlite is most basically perlite. If you see anything but little white rocks in it, or it says something is added, then stay away from it. For the most part i'd go with any perlite on the market except for if miracle gro made it. To tell you the truth, anything made or packaged in a plant that also processes things on the same equiptment that could have fertilizer, or other things that could hurt our plants can always possibly mix in at some point. Just like a chocolate bar without nuts in it might randomly have a nut somewhere in it.
The safest bet i've found with peat moss is to go for the larger, press dried bales over the smaller bags. Sometimes the smaller bags have wetting agents and other things mixed in, and if you've ever noticed the stuff is always a little moist when you open a fresh bag. Kind of a bad thing considering soil in a dark, humid, stagnant environment is a breeding ground for more things than I can count.
Schloaty,
Was that the stuff we kept finding osmocote pellots in?