As a swelling clay, bentonite has the ability to absorb large quantities of water, which increases its volume by up to a factor of eight. This makes bentonite beds unsuitable for building and road construction. However, the swelling property is used to advantage in drilling mud and groundwater sealants. The montmorillonite making up bentonite is an aluminum phyllosilicate mineral, which takes the form of microscopic platy grains. These give the clay a very large total surface area, making bentonite a valuable adsorbent. The plates also adhere to each other when wet. This gives the clay a cohesiveness that makes it useful as a binder and as an additive to improve the plasticity of kaolinite clay used for pottery.