Crystal chemistry of epsomite from three Bulgarian localities

Epsomite - MgSO₄•7H₂O has been first described as early as the eighteenth century and has attracted the interest of scientists for four centuries. Epsomite can be a constituent of evaporite mineral deposits and occurs as crusts and efflorescences in mine workings, in caves, in oxidation zones of sulphide ore deposits, on the surface of soils, and on the surface of objects of archaeological value. The so far published information on epsomite from Bulgarian deposits is based solely on microscopic and X-ray phase analyzes. In the present study, data on the crystal structure, spectroscopic and thermal characteristics of epsomite from three Bulgarian localities are reported for the first time. Data on natural compounds of the type (Mg_1-x,Zn_x)SO₄•7H₂O (0.03<x<0.36) are also presented for the first time. The impact of impurity elements on certain crystal structural characteristics and in particular on the metal octahedron are discussed and this polyhedron degree of deformation has been estimated.