Bronze colored microcrystals of the very rare mineral djerfischerite from this famous Russian locality: Rasvumtchorr, Khibiny, Kola, Russian Federation. It is one of the very few sulphides containing potassium. Djerfisherite in appreciable crystals is very rare. — Photo: David Hospital · CC BY-SA 4.0
Djerfisherite
An alkali copper-iron sulfide of complex, variable composition found in magmatic sulfide deposits.
Intro adapted from Wikipedia (CC BY-SA).
Djerfisherite is an IMA-recognized mineral species in the sulfide class, with the chemical formula K₆(Fe,Cu,Ni)₂₅S₂₆Cl.
It crystallizes in the cubic crystal system (space group Pm-3m). It is a member of the Djerfisherite structural group.
Key properties: Mohs hardness 3.5; Submetallic. R: (400) 17.5, (420) 18.3, (440) 19.1, (460) 20.0, (480) 20.8, (500) 21.6, (520) 22.3, (540) 22.9 luster.
IMA symbol Djr, IMA status: approved, named in 1965.
Found in meteorites, in hydrothermal Cu–Ni sulfide ores, in skarns, in pegmatites, in kimberlites, and alkalic mafics.
It is found associated with “Nickel-iron” (kamacite), troilite, schreibersite, clinoenstatite, tridymite, cristobalite, daubréelite, graphite, roedderite.
The mineral was named to honor Professor Daniel Jerome Fisher (1896–1988), American mineralogist, University of Chicago, Chicago, USA.