Vermiculite is another mined material. In its natural state it resembles mica rock, but when quickly heated it expands due to the generation of inter laminar steam. It has the capacity to provide a lot of humidity. It's often used as a seed covering. In fact, growers usually mix vermiculite with perlite. This is because vermiculite also has the ability to store plenty of nutrients. The main benefit of Vermiculite is that it holds on to nutrient, even when over-watered. It tends to be used for propagation in combination with other growing media. Vermiculite has the excellent property of improving soil aeration while retaining the moisture and nutrients necessary to feed roots, cuttings, and seeds for faster growth. Like perlite, vermiculite is permanent, clean, odorless, nontoxic and sterile. It will not deteriorate, turn moldy or rot. The pH of vermiculite is essentially neutral (7.0-9.5) but owing to the presence of associated carbonate compounds, the reaction is normally alkaline. It also will vary (become more alkaline) with changes in processing techniques and time, and with the presence of moisture. The pH, color and chemical composition of vermiculite also will vary from mine to mine. It is a well recognize hydroponics media. It is ideal for the germination of seeds. It has aeration properties and excellent water holding capacity which makes it an excellent medium for direct contact with seed.
