Hallangenite

Hallangenite is a rare and distinctive mineral belonging to the sorosilicate group, characterized by its unique chemical composition and striking appearance. It was first identified in 1976 in the Hallangen area of Norway, near the town of Røros, from which it derives its name. The mineral was officially recognized and named by the International Mineralogical Association in 1981. Hallangenite has the chemical formula Ca₄Mn₆²⁺Si₆O₂₄(SO₄)₂(OH)₄·12H₂O, indicating its complex structure, which includes calcium, manganese, silicon, sulfur, oxygen, and water molecules.

The mineral typically forms as dark brown to black, elongated prismatic crystals that often exhibit a fibrous or columnar habit. Its luster ranges from vitreous to silky, and it has a hardness of approximately 4.5 on the Mohs scale, making it relatively soft compared to many other minerals. Hallangenite is associated with hydrothermal veins and can be found in low-temperature, oxidized environments, often alongside other manganese-rich minerals such as rhodochrosite, calcite, and barite.

Due to its rarity, hallangenite is not commonly encountered in collections or research. Specimens are primarily sourced from its type locality in Norway, where it occurs in association with manganese ores. The mineral’s occurrence is limited to a few other locations worldwide, including parts of Russia and possibly some lesser-known deposits. Its scientific study contributes to the understanding of manganese-rich hydrothermal processes and the formation of secondary minerals in oxidized environments.

While hallangenite is not significant in industrial applications, its unique crystal structure and composition make it of interest to mineralogists and collectors. Research into its properties may also provide insights into broader geological processes involving manganese and sulfate minerals.