- A needle-like clay mineral composed of magnesium-aluminum silicate. Major deposits occur naturally in Georgia, USA. Attapulgite and sepiolite have similar structures and both can be used in saltwater mud to provide low-shear rate viscosity for lifting cuttings out of the annulus and for barite suspension. Attapulgite and sepiolite are sometimes called "salt gel." Attapulgite has no capability to control the filtration properties of the mud. For use as an oil mud additive, the clay is coated with quaternary amine, which makes it oil-dispersible and provides gel structure but does not improve the filter cake, unlike organophilicbentonite clay.
- shear rate