New Arsenate Mineral Belmonteite Discovered in Ligurian Manganese Ores

A team of researchers has announced the discovery of an unknown arsenate mineral named Belmonteite, with the chemical formula CaMn₂(AsO₄)₂(H₂O)₅·2H₂O. It was isolated from manganese ore deposits located in the Graveglia Valley of eastern Liguria, Italy. The study appears in volume 38 of the European Journal of Mineralogy, pages 531–543, published in 2026. ¹

The crystal structure of Belmonteite features {010} layers composed of six‑fold coordinated manganese atoms. These sites are flanked on both sides by (AsO₄) groups and calcium atoms, forming a layered arrangement further stabilized through hydrogen bonding between water molecules. This structural motif highlights interactions between metal cations and polyatomic anions within the lattice. ¹

Geochemical analysis indicates that the genesis of Belmonteite relates to circulation of As-rich oxidizing fluids percolating through the manganese ore system. Such fluid activity can introduce As into the host rock, leading to precipitation of new minerals under suitable pressure and temperature conditions. The authors note that this process mirrors similar arsenate formations observed in other hydrothermal environments worldwide. ¹

The discovery team—Cristian Biagioni, Jiří Sejkora, and Zdeněk Dolníček—has chosen to honor Donato Belmonte for his extensive contributions to the mineralogical knowledge of Ligurian geology. By naming the new species after him, they acknowledge his role in mapping the region’s diverse mineral assemblages. ¹

Although Belmonteite has not yet been reported outside academic circles, its identification adds another member to the growing list of rare arsenates found in manganese-rich terrains.

European Journal of Mineralogy has documented a novel mineral species from Italy that expands our understanding of arsenate chemistry within manganese ores.