Dark green-brown crystals of the rare amphibole mineral ferrian eckermannite from the type locality in Myanmar: Tawmaw, Hpakant Township, Mohnyin District, Kachin State, Myanmar. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Eckermannite
Eckermannite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaNa₂(Mg₄Al)Si₈O₂₂(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Amphibole structural group.
Key properties: Mohs hardness 5–6; specific gravity 3.02; [Vitreous.] luster; optically biaxial.
IMA symbol Eck, IMA status: approved, named in 2015.
Found in a jadeitite-amphibole fels rock, likely formed under blueschist facies conditions.
It is found associated with Jadeite, albite.
The mineral was named to honor Professor Claes Walther (Harry) von Eckermann (1886-1969), petrologist, Stockholm, Sweden.