Blue crystals of centennialite (IMA 2013-110) associated to minoritary green calumetite both associated to perfect halite cubes. Rudna Mine, Lubin District, Lower Silesia, Poland. — Photo: David Hospital · CC BY-SA 4.0
Centennialite
Centennialite is an IMA-recognized mineral species in the halide class, with the chemical formula CaCu₃Cl₂(OH)₆·nH₂O (n ~ 0.7).
It crystallizes in the hexagonal crystal system (space group P-3m1). It is a member of the Atacamite structural group.
Key properties: specific gravity 3.1.
IMA symbol Cte, IMA status: approved, named in 2013.
A secondary low-temperature mineral formed by the reaction of acidic water with other copper mineralization and essentially physically indivisible from other copper-containing secondary minerals.
It is found associated with Calumetite, atacamite family minerals (paratacamite, clinoatacamite).
The name refers to the Centennial mine, Calumet, Houghton County, Michigan, USA.