I was always confused between the two, buying it online (which I need to do here) made it more important that I figure it out. One of the things I need to know about any soil additive is whether it floats or not, many of my potted plants are pond plants and it is a major pain to have a bunch of stuff floating out of the pots. Perlite floats - it will work its way out of the deepest pot. Vermiculite doesn't float if it is well soaked before putting in the pond. Mostly I just remember that the white stuff floats, the beige not so much.
