Triploidite is an uncommon manganese phosphate mineral : (Mn. It crystallizes in the monoclinic and typically occurs as elongated and striated slender prisms which may be columnar to fibrous. Its crystals may be pinkish to yellowish brown or red-orange.
It was first described in 1878 for an occurrence in the Branchville Quarry, Branchville , Fairfield County, Connecticut. The name is derived from its resemblance to triplite
It typically occurs as a hydrothermal alteration product of primary phosphate minerals in granite pegmatites, lithiophilite, dickinsonite
It forms a solid solution series with the iron rich wolfeite