CaCu4(OH)8Cl2·3.5H2O (IMA proposal 18-C) to halides of copper

 

Calumetite (former "Vondechenite"*) embedded in a white jennite-thaumasite matrix from Bellerberg volcano.
Original find by Dr Christof Schäfer, analyzed and published. In the past this mineral was described as "UM Ca-Cu-Cl - mineral" and later "Vondechenite". In 2019 IMA redefined it to Calumetite.

You will not find often copper in a volcanic xenolithe; it results from Devonian Rhenish slate Mountain under the volcano were hydrothermal cracks are filled with quartz and ores. The azur blue halides have an orthorhombic structure. In same xenolithe Dr Schäfer found also some aggregates of Scottyite.

To avoid mistakes in lab all analysis had been done double. See other pictures in MinDAT.org. Near Scottyite you will find more sodalite and calcite environment.    

* see Schlüter, J., Malcherek, T., Pohl, D. and Schäfer, C. - 2016, Vondechenite, IMA 2016-065 CNMNC Newsletter No. 34, December 2016, Mineralogical Magazine, 80

IMA No. 2016-065 

·       CNMNC Newsletter No. 49, June 2019, page xxx; Mineralogical Magazine, 83, 323–328.