Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay. Montmorillonite is a typical weathering of aluminosilicates and one of the main minerals in many soils. Montmorillonite is the main component of bentonite that found in many sedimentary rocks. Due to its high adsorption properties, montmorillonite is used in the oil, textile, paper, and soap industries as an active component of bleaching and cloth clay. Montmorillonite is used in the oil drilling industry as a component of drilling mud, making the mud slurry viscous, which helps in keeping the drill bit cool and removing drilled solids. It is also used as a soil additive to hold soil water in drought-prone soils, used in the construction of earthen dams and levees, and to prevent the leakage of fluids. It is also used as a component of foundry sand and as a desiccant to remove moisture from air and gases. Montmorillonite is effective as an adsorptive of heavy metals and has been used and eaten from ancient time till now. For external use, montmorillonite has been used to treat contact dermatitis and in the materials produced for orthopedics, traumatology, dentistry.