Chalcomenite Locality: El Dragón mine, Antonio Quijarro Province , Potosí Department , Bolivia ( Locality at mindat.org ) Picture width 4 mm. Collection and photograph Christian Rewitzer — Photo: Christian Rewitzer · CC BY-SA 3.0
Chalcomenite
Chalcomenite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Cu(Se⁴⁺O₃)·2H₂O.
It crystallizes in the orthorhombic crystal system (space group P2_12_12_1).
Key properties: Mohs hardness 2–2.5; specific gravity 3.35; Vitreous luster; optically biaxial.
IMA symbol Ccm, grandfathered status — known before the IMA’s founding, named in 1881.
Found as a rare secondary mineral in oxidized Cu–Se-bearing deposits.
It is found associated with Umangite, clausthalite, molybdomenite, schmiederite (Cerro de Cacheuta, Argentina); penroseite, cobaltomenite, molybdomenite (Hiaco mine, Bolivia); allophane.
Its name comes from the Greek for copper and moon.