A THERMODYNAMIC ANALYSIS OF THE DECREPITATION PROCESS

The decrepitation properties of the two typical boron minerals coleman ite and ulexite reveal that, whereas colemanite undergoes decrepitatio n, ulexite shows no sign of significant fragmentation upon heating. Th is process enables separation of colemanite from ulexite at temperatur es above 400 degrees C. A thermodynamic evaluation of 14 boron mineral s has shown that only colemanite exhibits decrepitation. A mechanism i nvolving the temperature differential at the onset of dehydration and decomposition and the resultant enthalpy change is proposed as being r esponsible for this intriguing phenomenon.