perlite

Perlite is a naturally occurring, amorphous volcanic glass produced when rhyolitic lava with significant water content cools rapidly. When exposed to high temperatures, the hydrated glass expands as the trapped water vaporizes, creating a porous, lightweight material known as expanded perlite. Expansion typically occurs at around 760 to 1,000 degrees Celsius, yielding a cellular structure that is inert and stable.

Expanded perlite is widely used in horticulture and agriculture as a soil amendment and growing medium. Its high porosity improves aeration and drainage while retaining some moisture, helping prevent soil compaction. It is commonly blended with peat, compost, or coco coir, and is also employed in hydroponic systems and seed starting mixes. Beyond gardening, perlite serves as a loose-fill insulation, fireproofing agent, and filler in construction products due to its low density and insulating properties. It can be milled into powders or granules for specialty applications such as filtration and soundproofing.

Natural perlite is an aluminosilicate glass with approximately 70–75% silicon dioxide and 12–14% aluminum oxide, along with minor amounts of other oxides. It is mined in several countries, then crushed and sorted before undergoing the expansion process. Expanded perlite is inert, chemically neutral, and non-toxic, making it suitable for many horticultural uses, though handling precautions are advised to minimize dust exposure.

Safety and environmental notes: dust can irritate the eyes, nose, and lungs, so moisture or personal protective equipment is recommended when handling dry material. The production process requires energy input, but the material itself is stable and low in toxicity.