Finely divided polysacharide derivatives are described. The finely divided polysacharide derivatives are prepared by a process comprising: a) forming an aqueous composition comprising a polysaccharide derivative and water, in which the polysaccharide derivative is soaked or dissolved; b) converting the polysaccharide derivative of the aqueous composition into finely divided solid particles by, (i) contacting the aqueous composition with superheated water vapor in a dryer-pulverizer; or (ii) causing the polysaccharide derivative of the aqueous composition to flocculate; and c) optionally drying the finely divided solid particles of step b). The primary structures of the polysaccharide starting material are largely removed, and the product has a shape factor of less than 5 and greater than or equal to 1.