What Is Vermiculite Soil?
Plants need rich, well-drained soil to thrive, and vermiculite can help boost their growing medium. Although vermiculite is often packaged with potting soil mixes, it is not a type of soil at all. Instead, vermiculite is a mineral that resembles mica. When treated with intense heat, vermiculite expands into lightweight particles containing many layers. The particles help lighten heavy soils and the layers hold moisture and nutrients, helping plants grow.
Features
Vermiculite's technical name is hydrated laminar magnesium-aluminum-iron silicate. In its natural state, vermiculite takes the form of layered, flat sheets like mica. Heating vermiculite exfoliates, or expands, the layers eight to 30 times their original size. The heating process creates small accordion-pleated nuggets about a half-inch long that are lightweight and absorbent.
Function
Gardeners can use vermiculite to lighten and aerate heavy soil, root cuttings, germinate seeds or mulch around outdoor plants and shrubs. Vermiculite also helps keep soil in house plants pots well-drained. You can purchase vermiculite alone or packaged as potting soil along with peat moss or perlite, another mineral.
Benefits
Vermiculite is non-toxic, odorless and sterile. It will not mold or rot. Its absorbent properties allow it to retain ammonium, potassium, magnesium and calcium that plants need. Mixed with peat or composted pine bark, it makes an excellent vehicle for holding moisture and plant food. Vermiculite also mixes well with pesticides and herbicides.
Geography
Vermiculite mining takes place around the world. Australia, China, Brazil, South Africa, Zimbabwe, Kenya and the United States are the largest suppliers of vermiculite. Most of the mines are surface operations in which the vermiculite is separated from other ores. One of the largest vermiculite mines, the Libby mine in Libby, Montana, operated from 1920 to 1990.
Types
In addition to gardening and horticulture, vermiculite is used in agriculture, construction and manufacturing. You can find vermiculite in animal feed, sound-proofing material, insulation, and brake pads and shoes. Vermiculite is also combined with gypsum plaster, resins and cement. In potting soil, it looks like silver or gold flakes.
Considerations
A 2000 Environmental Protection Agency study found that some vermiculite gardening products contained asbestos. The EPA did the study after vermiculite produced by the Libby mine was found to contain asbestos. The agency concluded, however, that the risk to consumers is minimal. The EPA does recommend using vermiculite in a well-ventilated area and keeping the product moist to minimize possible asbestos exposure.
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