Montmorillonite 2 : A clay mineral commonly used as an additive to drilling fluids. Sodium montmorillonite is the main constituent in bentonite. (Bul 10C)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}