Mackinawite Locality: Kirovskii apatite mine (Kirovsky Mine; Kirov Mine), Kukisvumchorr Mt, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia Field of view 4 mm. Specimen and photo Leon Hupperichs. — Photo: Leon Hupperichs · CC BY-SA 3.0
Mackinawite
An iron-rich, sulfur-deficient iron monosulfide — often the first sulfide to precipitate in anoxic sediments.
Intro adapted from Wikipedia (CC BY-SA).
Mackinawite is an IMA-recognized mineral species in the sulfide class, with the chemical formula (Fe,Ni)₁₊ₓS (x = 0-0.07).
It crystallizes in the tetragonal crystal system (space group P4/nmm).
Key properties: specific gravity 4.3; Black streak; Metallic luster.
IMA symbol Mkw, IMA status: approved, named in 1964.
Formed by hydrothermal activity in mineral deposits, during serpentinization of peridotites, and in the reducing environment of river bottom muds; may be produced by magnetotactic and sulfate-reducing bacteria.
It is found associated with Chalcopyrite, cubanite, pentlandite, pyrrhotite, greigite, maucherite, troilite.
The name refers to the Mackinaw mine in Washington, USA.