New Arsenate Mineral Belmonteite Discovered in Italian Mn Deposits

A team led by Cristian Biagioni has announced the discovery of a previously unknown arsenate mineral named Belmonteite (CaMn₂(AsO₄)₂(H₂O)₅·2H₂O). The find comes from manganese ore outcrops in the Graveglia Valley of eastern Liguria, Italy, and was published on 2026-02-01 in the European Journal of Mineralogy ¹.

The crystal lattice is built around {010} planes that host six‑fold coordinated manganese atoms. Each plane is flanked by (AsO₄) tetrahedra and calcium ions; hydrogen bonds link these layers into an extended framework. This arrangement gives Belmonteite its distinctive structural signature, setting it apart from other known arsenates ¹.

Geochemical analysis indicates that Belmonteite formed when As-rich oxidizing fluids migrated through the manganese deposit, depositing arsenic. Such fluid pathways are typical for Mn ore bodies in Liguria but have not been documented to produce this particular mineral composition before now ¹.

The species name honours Donato Belmonte, whose research advanced understanding of Ligurian mineralogy. By naming the new mineral after him, the authors acknowledge his longstanding contributions to regional studies ¹.