Reading the article and all the comments made me curious about perlite. I had always thought that perlite was naturally occurring pumice. No. Perlite is a naturally occurring volcanic glass that is ground and then popped like popcorn (if your popcorn popper heated to 1600F).
Here is a site with more information on all it's many uses.

http://www.perlite.net/

Yep, as the article says, perlite comes from super-heating volcanic glass. You show a good site for more information.