The crystal structure of synthetic konyaite, Na2Mg(SO4)2·5H2O, a = 5.7690(8), b = 23.951(3), c = 8.0460(11) Å, β = 95.425(2)°, V = 1106.8(3) Å3, space group P21/c, Z = 4, was solved using single-crystal X-ray diffraction. Hydrogen atom positions were determined and the structure solution was refined to R1 = 3.31% and wR2 = 6.28% for the 2167 measured independent reflections. Three distinct cation sites host the Mg and Na atoms in distorted octahedra and eight-coordinated polyhedra. The coordination polyhedra share edges to form compact sheets oriented perpendicular to b and linked to one another by hydrogen bonds. This results in a {010} tabular habit. A comparison of this structure is made to that of blödite [Na2Mg(SO4)2·4H2O], the dehydration product of konyaite. Konyaite is discussed within the context of the Na2O-MgO-SO4-H2O system. This study is part of ongoing investigations into the dehydration mechanisms and phase stability of this system.

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