Perlite

Perlite ore is an inorganic, naturally occurring mineral. More specifically it is a glassy siliceous volcanic rock. When heated to fusion temperature, the molten grains expand into lightweight multicellular particles four to twenty times their original volume. The resulting particles are sized and graded for specific uses, the most common of which are masonry block fill and attic insulation. No special equipment is needed when using this lightweight product. As loose-fill masonry insulation, it offers excellent thermal and fire-resistant properties at an economical cost. Significant energy savings have been reported with use in cavity-fill applications.