Experiments have been carried out in a hydrocyclone and a Vorsyl separator using fine magnetite particles (less than 75 mu m sizes). Although at all the experimental conditions "fish-hook" has been observed, the shape of the curves is found to be different. Therefore, in this paper a set of new nomenclature has been proposed to quantify the differences in various shapes. An attempt has also been made to describe the effects of variables on the shapes of "fish-hook" in terms of the proposed nomenclature. At a given operating condition, it is also shown that the shape of a "fish-hook" remains unchanged. (c) 2006 Elsevier Ltd. All rights reserved.