gerrya - isn't it interesting how different people have different experiences with the same thing? I have always found that, for me, perlite is the one that deteriorates and goes to powder inthe compost, wheras vermiculite remains inert for donkeys years!! Guess it doesn't really matter, neither appears to be made in a chemical laboratory and that will do for me, meanwhile we will stick to the product we know best. Happy, albeit very wet, gardening to all - with perlite or vermiulite as the fancy takes you.