Dark brown cystals of the very new and extremely rare mineral stefanweissite (IMA 2018-020) from the type and only known locality for the mineral: In den Dellen Quarries, Niedermendig, Mendig, Eifel, Rhineland-Palatinate, Germany. Stefanweissite is a rare earth-Zr-Nb-mineral. The name honours Dr. Stefan Weiss (b. 1955), German geologist, mineralogist and petrologist. He is the editor of the Lapis magazine, a famous German mineral magazine. — Photo: David Hospital · CC BY-SA 4.0
Stefanweissite
Stefanweissite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Ca,REE)₂Zr₂(Nb,Ti)(Ti,Nb)₂Fe²⁺O₁₄.
It crystallizes in the monoclinic crystal system (space group Cmca). It is a member of the Zirconolite structural group.
Key properties: specific gravity 5.254; Light brown to yellow streak; Adamantine luster.
IMA symbol Swi, IMA status: approved, named in 2018.
Found in cavities inside sanidinite volcanic ejecta.
It is found associated with Sanidine, nosean, biotite, augite, titanite, ferriallanite- (La), magnetite, baddeleyite, a pyrochlore-group mineral.
The mineral was named to honor PhD Stefan Weiss (b. 1955), German geologist, mineralogist, petrologist, and editor of LAPIS magazine since May 1993.