Belmonteite: New Arsenate Mineral Found in Liguria Ore Deposits

In 2026, researchers Cristian Biagioni, Jiří Sejkora, and Zdeněk Dolníček reported the identification of a previously unknown mineral named belmonteite (CaMn₂(AsO₄)₂(H₂O)₅·2H₂O) ¹.

The specimen was recovered from manganese ore deposits in Graveglia Valley of eastern Liguria, Italy ¹. The newly described species incorporates both calcium and manganese atoms within its lattice. Its empirical formula—CaMn₂(AsO₄)₂(H₂O)₅·2H₂O—highlights a complex arrangement where two AsO₄ tetrahedra coordinate to six‑fold Mn centers while hydrogen bonds link the structure through interstitial water molecules ¹.

X‑ray diffraction analysis revealed that the crystal adopts a layered architecture along the {010} plane. These layers consist of alternating sheets of six‑coordinated Mn atoms, flanked on each side by (AsO₄) groups and Ca ions. Hydrogen bonding between these components stabilizes the overall framework ¹.

The mineral was named after Donato Belmonte, a prominent geologist whose work has substantially advanced understanding of Ligurian mineralogy. By honoring him, the authors emphasize the regional significance of this discovery and its contribution to the broader catalog of Italian ore minerals ¹