A white clay (especially a white clay used by potters).

Roget 324: softness, pliableness etc. adj.; flexibility; pliancy, pliability; sequacity^†, malleability; ductility, tractility^†; extendibility, extensibility; plasticity; inelasticity, flaccidity, laxity.    penetrability.    clay, wax, butter, dough, pudding; alumina, argil; cushion, pillow, feather bed, down, padding, wadding; foam.    mollification; softening etc. v.. ... meer laten zien