The where of mineral names: Merelaniite, Merelani (Mererani), Manyara region, Tanzania

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MERELANIITE, named after the village of Merelani “in honor of the local miners, past and present, living and working in the region” (Jaszczak et al. 2016, p. 115), is a rare and interesting sulfide mineral from the tanzanite mines in Tanzania, eastern Africa. Merelaniite from Tanzania was actually first noted but not so named in the literature by Jessica Simonoff and Michael Wise (2012a, b), who described the cylindrical whiskers associated with prehnite and chabazite as an unusual occurrence of filiform molybdenite. Subsequent investigations, however, showed it to be a new triclinic mineral with a composition of approximately Mo4Pb4VSbS15 (Jaszczak et al. 2016). Additional elements that can substitute into the crystal structure include Bi, As, Mn, W, Cu, and Se. Merelaniite is a member of the cylindrite group and forms dark gray cylindrical whiskers with a metallic luster. They are typically tens of micrometers in diameter and up to 1 or a few millimeters long, although rarely they can reach over 10 mm long. Like cylindrite, merelaniite is composed of alternating pseudohexagonal and pseudotetragonal layers that are strained relative to each other. In merelaniite, the pseudohexagonal layer is predominantly MoS2, whereas the pseudotetragonal layer is composed of two atomic layers of primarily PbS.

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Rocks and Minerals