Mackinawite - Encyclopedia
Class : Sulfides and sulfosalts
Subclass : Sulfides
Crystal system : Tetragonal
Chemistry : (Fe,Ni)9S8
Rarity : Uncommon
Mackinawite is a nickel and iron sulfide widely distributed but always in very small quantities. It is a hydrothermal mineral observed in many high temperature copper or nickel deposits, and which also crystallizes during the serpentinization of peridotites. It is also found in certain meteorites. Its name comes from its location of discovery : the Mackinaw mine (Washington, USA). Machinawite very rarely occurs in automorphic lamellar crystals and almost exclusively forms very fine exsolutions, resembling flames or lamellae, in other sulfides, mainly chalcopyrite. It is bronze in color.
Main photo : Mackinawite (luminous white) in exsolution in twinned chalcopyrite from Akjoujt, Mauritania © Paul Picot
Mackinawite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 2.5
Density : 4.17
Fracture : Undetermined
Streak : Black
TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None
Solubility : -
Magnetism : NoneRadioactivity : None