Vermiculite takes the form of crystalline layers like mica.
Vermiculite is a hydrated basaltic mineral with some unusual properties that have made it popular in industrial manufacturing since the early 20th century. Many consumers are likely to interact with vermiculite as it is used as a filler in a wide range of products and can also be found in materials such as insulation, absorbent materials and soil mixes. Direct contact with vermiculite is relatively rare as it is used as a component rather than a main ingredient, although people who work with some forms of insulation can handle vermiculite.
Vermiculite is a hydrated basaltic mineral.
There are two interesting things about vermiculite that make the mineral desirable to manufacturers. The first is its physical structure, which takes the form of crystalline layers such as mica. The second is the water trapped within the vermiculite. If the mineral is heated, the water turns to steam, forcing the mineral to expand, and the layers unfold like an accordion, creating strands of very light, porous material. When vermiculite is used, it is usually heated to expand it, in a process known as exfoliation.
The name “vermiculite” is derived from the Latin word for worm, a reference to the strands of vermiculite material that form when vermiculite is exfoliated. This property was well known to people in the 19th century, although it was treated as a novelty rather than a potentially useful mineral until people realized its potential for things like insulation and concrete mixing. The mineral was named, by the way, by Thomas Webb in 1924. It’s more formally known as hydrated magnesium-aluminum-iron layered iron silicate, which is quite complicated.
Some people have raised health concerns about vermiculite. The mineral itself is not harmful, but it often contains unhealthy impurities, such as asbestos. Additionally, the exfoliation process can generate silicate fibers that can be dangerous to inhale. As removing impurities from the mineral is not really feasible, people should handle vermiculite with care to reduce potential exposure to health risks. When handling substances such as insulation, mouth and nose protection should be worn so that people do not inhale small silicate fragments that can damage their lungs.
Historically, one of the largest sources of vermiculite was a mine owned by WR Grace in Libby, Montana. Although this mine is now closed, vermiculite can be found in other regions of the United States, such as Virginia. There are also large mines in South Africa, China and Australia. Depending on where it is mined, the ore may have more or less impurities.