Kuliginite is a new iron-magnesium hydroxychloride mineral with the ideal formula Fe3Mg(OH)6Cl2 from the Udachnaya East kimberlite, Yakutia, Russia. It occurs as green prismatic-bipyramidal crystals (0.2–0.5 mm) and fills cavities and veins in several units of kimberlites together with iowaite, gypsum, calcite, halite, barite, and celestine. It is trigonal, with R3 space group. Kuliginite has imperfect cleavage on {1011}. The spinel-like crystal structure of kuliginite is also typical for several copper minerals of the atacamite group with common formula Cu3M(OH)6Cl2; kuliginite can be regarded as a Fe2+ analog of tondiite [Cu3Mg(OH)6Cl2].

The occurrence of the kuliginite + iowaite + gypsum assemblage has implications for the interpretation of low-temperature (below 100°C) hydrothermal processes and alteration of kimberlite by hydrothermal fluids/brines, as well as for transport of metals in Cl-bearing solutions. This secondary hydrothermal mineral assemblage formed much later than the kimberlite groundmass minerals. Kuliginite contains inclusions of iowaite indicating their simultaneous crystallization.

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