Vermiculite is the name of a group of hydrated laminar minerals (aluminium-iron magnesium silicates) that look like mica.
$54.00 for a 100Ltr bag
Horticultural vermiculite is processed with massive heat that expands it into accordion shaped pellets composed of multiple layers of thin plates. It will not rot, deteriorate, or mould and is enduring, odourless, non-toxic and sterile. Vermiculite is generally a neutral 7.0 pH but is dependent upon the source from around the globe and its reaction is alkaline. It is very lightweight and mixes easily with other mediums.
Vermiculite added to the garden or vermiculite in potting soil increases water and nutrient retention and aerates the soil, resulting in healthier, more robust plants. Perlite may also be found in potting soils, but vermiculite is far superior for water retention. Vermiculite, although less aerating than perlite, is the amendment of choice for water-loving plants. Here are other uses for vermiculite:
Read more at The Gardening Channel: What Is Vermiculite: Tips On Using Vermiculite Growing Medium