What type of material is vermiculite?

Vermiculite is indeed a type of volcanic rock. It is a naturally occurring mineral that expands when heated, giving it unique properties that make it useful in various applications, particularly in construction and insulation. When vermiculite is subjected to high temperatures, it expands to many times its original volume, creating a lightweight and insulative material.

This expansion process allows it to trap air within its structure, providing excellent thermal insulation and soundproofing qualities. Vermiculite is often used in insulation for attics and walls, as well as in soil amendments for gardening due to its ability to retain moisture and improve aeration.

The other options represent different materials that do not accurately describe vermiculite: artificial polymers are synthetic materials, mineral wool is a different type of insulation made from rock or glass fibers, and cellulose fibers come from plant sources, none of which relate to the volcanic origin and properties of vermiculite.