Vermiculite is a hydrous phyllosilicate mineral which undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently, and commercial furnaces can routinely produce this effect. Vermiculite forms by the weathering or hydrothermal alteration of biotite or phlogopite.
Calcium Phosphorus Potassium Magnesium Which are components that plants can utilize
Vermiculite can absorb three or four times its weight in water and also attracts various plant nutrients such as potassium, magnesium and calcium. These qualities make it useful for propagation and for potting up plants that do best in moist compost, including house plants.
Vermiculite is better for water and nutrient retention than perlite and is best used for plants that need more moisture to grow. Vermiculite also protects seedlings against damping-off and other fungal diseases.