In the case of milled samples (Fig. ), three mass loss events are observed: the first step, centered at 280°C, is related to crystallization water loss concomitant with physically adsorbed moisture elimination. The second step, centered at 420°C, is associated to partial structural water loss and structure dimerization, and the final step, centered at 710°C corresponds to final structural water loss reaction and structure polycondensation . In addition, all the samples milled at 600 rpm do not present of calcite decomposition below 700 °C but in the samples milled for 2 h at 400 rpm this event is still observed. It suggests that in low rotation speeds do not provide enough energy to degrade the total amount of calcite to form calcium potassium phosphates. It is observed that all samples processed at 600 rpm present a similar thermal decomposition, but with different residuals masses according to the milling time. Water loss at 340°C reduces with milling time probably due to water formation and adsorption during the process and subsequently desorption increasing time milling.