Vermiculite
/ver-MIK-yoo-lite/🪨 Soil Types● Basic
Also known as: expanded vermiculite
A group of hydrated laminar aluminium-iron-magnesium silicate minerals that expand dramatically when heated, creating lightweight, sponge-like granules. In horticulture, vermiculite is valued for its excellent water-holding capacity and cation exchange properties, making it useful in seed starting, potting mixes, and as a covering for seeds that require light to germinate. It retains more water than perlite but provides less aeration.
Etymology
Latin vermiculare (to breed worms), from the worm-like shape when heated
Example
“Cover fine seeds like lettuce with a thin layer of vermiculite — it retains moisture while allowing light through.”