Origin and Characteristics...

Perlite is not a trade name but a generic term for naturally occurring siliceous rock. The  distinguishing feature which sets perlite apart from other volcanic glasses is that when it is heated to a suitable point in its softening range, it expands from four to twenty times its original volume. This expansion is dues to the presence of two to six percent combined water in the crude perlite rock. When quickly heated to above 871°C (1600°F), the crude rock pops in a manner similar to popcorn as the combined water vaporizes and creates countless tiny bubbles which account for the amazing light weight and other exceptional physical properties of expanded perlite.

 This expansion process also creates one of perlite's most distinguishing characteristics: its white color. While the crude rock may range from transparent light gray to glossy black, the color of expanded perlite ranges from snowy white to grayish white.  Expanded perlite can be manufactured to weigh as little as (32kg/m3) making it adaptable for numerous applications in construction, industrial, chemical and horticultural. Since perlite is a form of natural glass, it is classified as chemically inert and has a pH of approximately 6.5 - 7.5.

Masonry Fill Brochure

Material Safety Data Sheet – Perlite (.PDF)  

Links:

The Perlite Institute Inc. The Perlite Institute is an international trade organization, dedicated to the perlite industry.

Midwest Perlite Inc.
4280 W. Parkway Blvd.
Appleton WI 54913-8231
920-731-3143