Perlite

Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an industrial mineral and a commercial product useful for its light weight after processing.

Perlite is a non-renewable resource. The world reserves of perlite are estimated at 700 million tonnes.

In horticulture, perlite can be used as a soil amendment or alone as a medium for hydroponics or for starting cuttings. When used as an amendment it has high permeability / low water retention and helps prevent soil compaction.

Perlite provides extremely efficient increase in aeration as a consequence of its high air filed pore space. It produces a well drained environment for root growth.