Vermiculite What is vermiculite? Vermiculite is a hydrous phyllosilicate mineral. It undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently, and the effect is routinely produced in commercial furnaces. Vermiculite is formed by weathering or hydrothermal alteration of biotite or phlogopite. What does this mean, it’s a mineral that exist in the ground. There are many use for vermiculite, but today we are going