Perlite

Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian.

It is an industrial mineral, suitable "as ceramic flux to lower the sintering temperature", and a commercial product useful for its low density after processing.

[6][7] Perlite world production, led by China, Turkey, Greece, USA, Armenia and Hungary, summed up to 4.6 million tonnes in 2018.

[citation needed] Small quantities of perlite are also used in foundries, cryogenic insulation, and ceramics (as a clay additive).

[citation needed] Due to thermal and mechanical stability, non-toxicity, and high resistance against microbial attacks and organic solvents, perlite is widely used in biotechnological applications.

When used as an amendment, it has high permeability and low water retention and helps prevent soil compaction.

Substitutes include:[20] As perlite contains silicon dioxide, goggles and silica filtering masks are recommended when handling large quantities.