Sulphate mineralization from one locality in Lozen ore field, Eastern Rhodopes

A suite of sulphates from a locality in Lozen ore field in the Eastern Rhodopes has been characterized by chemical analyses and X-ray diffraction. Three mineral species have been identified: epsomite (MgSO4), pickeringite (MgAl2(SO4)4•22H2O) and alunogen (Al2(SO4)3•17H2O). An attempt was made to characterize the phase transformations that occur upon wetting of the studied samples. The results show that at high humidity, pickeringite dissolves, providing constituents for subsequent crystallization of epsomite and alunogen. Further on, upon drying alunogen loses some of its crystallization water and recrystallizes again to pickeringite including magnesium species from the surrounding medium. This study draws light on certain genetic aspects related to the mechanisms and sequence of deposition of sulphate mineralization under similar conditions.