Zussmanite
A pale-green iron-rich potassium phyllosilicate with perfect cleavage.
Intro adapted from Wikipedia (CC BY-SA).
Zussmanite is an IMA-recognized mineral species in the silicate class, with the chemical formula K(Fe,Mg,Mn)₁₃(Si,Al)₁₈O₄₂(OH)₁₄.
It crystallizes in the hexagonal crystal system (space group R-3). It is a member of the Clay structural group.
Key properties: specific gravity 3.146; Vitreous luster; refractive index 1.633; optically uniaxial.
IMA symbol Zus, IMA status: approved, named in 1964.
Found in an exotic block of metamorphosed shales, siliceous ironstones, and impure limestones, probably representing deep ocean sediments subjected to blueschist facies metamorphism.
It is found associated with Deerite, howieite, stilpnomelane, spessartine, riebeckite, quartz, aegirine, grunerite, aragonite, manganoan siderite, ferroan kutnohorite, graphite.
The name refers to Jack Zussman (1924{), mineralogist-crystallographer, Manchester University, Manchester, England.