This technical contribution is aimed at studying the physicochemical properties of cashew gum as well as its performance as a limestone depressor during the phosphate minerals flotation. Cashew gum and starch characterizations were accomplished by identifying their functional groups through infrared spectroscopy. After that, some physicochemical properties of calcite were investigated, having cashew gum as a depressant, by using microflotation and flotation techniques. It was observed, by comparing the infrared spectra of both substances, that one was dealing with quite similar structures. The microflotation tests showed that flotability decreases as the cashew gum or starch concentrations increase. The flotation of limestone confirms the depressing power of cashew gum, showing that it is possible to reduce the insoluble residues (IR) from 10.5%, in the original ore, to near 0.6% with carbonate recovery in the range of 70-80%. (C) 2003 Elsevier Ltd. All rights reserved.