What is a perlite microsphere?

A perlite microsphere is a small, hollow, spherical particle that is extremely lightweight and produced by the thermal expansion of volcanic perlite. When heated to around 1200 °C, perlite expands like popcorn, forming a porous, multicellular structure.

This process creates a siliceous particle that is stable, naturally inorganic, inert, non-toxic, and pH-neutral.