Vermiculite is a naturally occurring mineral compound created by the hydrothermal alteration of biotite, phlogopite or chlorite. It mainly consists of hydrated silicate of Magnesium, Aluminium, Iron, Calcium and Potassium. Deposits can be found in continents around the world with South Africa, China and the USA being the largest exporters. It is mined using open cut techniques where the mineral is separated from other minerals and then classified into several basic particle sizes.
Vermiculite can expand up to thirty times its original size, between temperatures of 900ºC - 1100ºC, due to the interlaminar water-vapour pressure. This gives it its excellent thermal and acoustic insulatory properties. The material is beige in colour and has a soft spongy texture. Its formula is M0.75+ Al2(Si3.25Al0.75) O10(OH)2, where M+ represents exchangeable cations.
Exfoliated Vermiculite has a low density and is an excellent insulator making it ideal for the use in panels used in the construction of buildings. These boards are commonly used as the core in fire doors, fire-barriers, cladding for steel building elements and chimneys. Because of its high temperature resistance, and low price, it is also used widely in commercial products such as wood burning stoves, gas fires and boilers to insulate them. This increases their efficiency and reduces the amount of heat lost during operation.
Vermiculite is used extensively throughout the agriculture industry as well as for the use in gardening. The highly absorbent vermiculite flakes improve aeration and water retention of the soil creating the ideal conditions for plant growth. Its absorbency also makes it a popular additive in animal feed, as a medium for holding nutrients.
Although mined, Vermiculite is commonly found at surface level which means that its extraction does not require tunneling. And even though the demand of Vermiculite has risen in the last century, the mineral can be found in abundance all over the world, suggesting that is has not been mined irresponsibly. Although not biodegradable, Vermiculite fertilizer can be left in the ground, and will continue to release potassium and magnesium into the soil for years to come
Hydroponic farming has become increasingly popular in recent years, and has been shown to produce a higher yield whilst using less water, space and energy than traditional soil-based farming. Vermiculite has become a common growth-medium used in hydroponics, often mixed with perlite or coir.
Vermiculite has proven to be a promising medium for antibacterial or antimycotic compounds as its layer-charge is greater than that of the commonly used montmorillonite. Researchers used a vermiculite and Carboxymethylcellulose nanocomposite as a carrier of chlorhexidine for the treatment of oral stomatitis. Nanoclays are being widely investigated for their potential in drug delivery for their biocompatibility, high specific surface area and chemical inertness.