Attapulgatite Clay : A colloidal, viscosity-building clay used principally in salt-water drilling fluids. Attapulgite, a special fullers earth, is a hydrous magnesium aluminum silicate. (Bul D11)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}