This International Standard covers physical properties and test procedures for materials manufactured for use in oil- and gas-well drilling fluids. The materials covered are barite@ haematite@ bentonite@ nontreated bentonite@ OCMA grade bentonite@ attapulgite@ sepiolite@ technical grade low-viscosity carboxymethylcellulose (CMC-LVT)@ technical grade high-viscosity carboxymethylcellulose (CMC-HVT)@ and starch. This International Standard is intended for the use of manufacturers of named products.