triploidite

Triploidite is a rare phosphate mineral with the chemical formula (Mn,Fe)5(PO4)2(OH)2. It is a member of the triploidite group, which also includes wolfeite and serendibite. Triploidite typically occurs as prismatic to acicular crystals, often found in granular or massive aggregates. Its color can range from pale yellow to reddish-brown or brown.

The mineral was first discovered in 1877 in Långban, Sweden. It is found in metamorphosed iron and manganese deposits, often associated with other phosphate minerals and iron and manganese oxides. Notable occurrences besides Långban include Franklin and Sterling Hill in New Jersey, USA, and various locations in Brazil.

Triploidite is a relatively soft mineral, with a Mohs hardness of around 4.5 to 5. It has a specific gravity of approximately 3.6 to 3.8. The crystal structure of triploidite is characterized by chains of Mn/Fe octahedra linked by phosphate tetrahedra and hydroxyl groups. The presence of both manganese and iron in its formula contributes to the variation in its color and physical properties. Due to its rarity and often small crystal size, triploidite is primarily of interest to mineral collectors and researchers studying metamorphic mineral paragenesis. It is not used in any industrial applications.