Mackinawite

Mackinawite
Mackinawite
General
Category	Sulfide mineral
Formula (repeating unit)	(Fe,Ni)1 + xS (where x = 0 to 0.11)
Strunz classification	02.CC.25
Crystal symmetry	Tetragonal 4/m 2/m 2/m
Unit cell	a = 3.67 Å, c = 5.03 Å; Z=2
Identification
Formula mass	85.42 g
Color	Bronze to white grey
Crystal habit	As well-formed thin tabular crystals; massive, fine-feathery
Crystal system	Tetragonal - ditetragonal dipyramidal
Cleavage	Perfect on {001}
Mohs scale hardness	2.5
Luster	Metallic
Streak	Black
Diaphaneity	Opaque
Specific gravity	4.17
References	[1][2][3]

Mackinawite is an iron nickel sulfide mineral with formula (Fe,Ni)_{1 + x}S (where x = 0 to 0.11). It crystallizes in the tetragonal crystal system and occurs as opaque bronze to grey-white tabular crystals and anhedral masses. It has a Mohs hardness of 2.5 and a specific gravity of 4.17.

Occurrence

It occurs in serpentinized peridotites as a hydrothermal alteration product. It also is found in the reducing environment of fine grained river sediments, possibly produced by the action of magnetotactic and sulfate-reducing bacteria. It has also been reported from meteorite occurrences. It occurs in association with chalcopyrite, cubanite, pentlandite, pyrrhotite, greigite, maucherite and troilite.^[1]

It was first described in 1962 for an occurrence in the Mackinaw mine, Snohomish County, Washington for which it was named.^[3]

See also

• Glossary of meteoritics

References