Chlorartinite, a volcanic exhalation product also found in industrial magnesia screed

The volcanic exhalation product chlorartinite, [Mg 2 (CO 3 )(H 2 O)(OH)]Cl·H 2 O, has recently been found to be a minor, and in some samples a major, component of magnesia floors for industrial use. In order to be able to perform quantitative phase analysis using the Rietveld method, its crystal structure was determined from high-resolution synchrotron powder diffraction data by the global optimization technique of simulated annealing and Rietveld refinement. The final R p and R wp values are 5.23% and 6.56%, respectively. Chlorartinite crystallizes in the rhombohedral space group R 3 c (No. 161), with a = 23.14422 (16) Å, c = 7.22333 (5) Å, V = 3350.84 (5) Å 3 , Z = 18. The building units of chlorartinite consist of MgO 6 octahedra forming 15-membered puckered rings which are interconnected by CO 3 triangular moieties. The rings are stacked to form a honeycomb-like three-dimensional framework structure with large isolated channels. Within the channels, free chlorine atoms and disordered water molecules are located.