Djerfisherite

Djerfisherite is an alkali copper–iron sulfide mineral and a member of the djerfisherite group.

Djerfisherite
Djerfisherite found in Russia
General
Category	Sulfide mineral
Formula (repeating unit)	See text
Strunz classification	2.FC.05
Crystal system	Cubic
Crystal class	Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m)
Space group	Pm3m
Unit cell	a = 10.465 Å; Z = 1
Identification
Color	Greenish yellow, khaki to olive drab
Crystal habit	Rounded grains
Mohs scale hardness	3.5
Luster	Submetallic
Diaphaneity	Opaque
Optical properties	Isotropic
References	[1][2][3]

The chemical composition is somewhat variable. A Russian study from 1979 on djerfisherite from the Kola Peninsula found the formula K
₆Na(Fe,Cu)
₂₄S
₂₆Cl, but a study in 2007 of a samples from Siberia found no detectable sodium and states that the formula K
₆(Fe,Cu,Ni)
₂₅S
₂₆Cl is considered the most appropriate.[4] Both crystallographic studies have 58 atoms per unit cell. Sulfur atoms are in three nonequivalent locations, containing 12, 6, and 8 atoms per unit cell. The later study put a copper atom where the earlier study put a sodium atom.[5] More information on the structure and other questions is available,[4] as well as 3-D models.[1]

The Webmineral "Mineralogy Database" site gives the "chemical formula" as K
₆Na(Fe²⁺
,Cu,Ni)
₂₅S
₂₆Cl, apparently in error, and an "empirical formula" as K
₆NaFe²⁺
₁₉Cu
₄NiS
₂₆Cl.[3]

Its type locality is the Kota-Kota meteorite (Marimba meteorite), Malawi. It was first described in 1966 and named after professor Daniel Jerome Fisher (1896–1988), University of Chicago.[1] It has been reported from meteorites, copper-nickel hydrothermal deposits, skarn, pegmatite, kimberlites and alkalic intrusive complexes. Associated minerals include kamacite, troilite, schreibersite, clinoenstatite, tridymite, cristobalite, daubreelite, graphite, roedderite, alabandite, talnakhite, pentlandite, chalcopyrite, magnetite, valleriite, sphalerite and platinum minerals.[2]