Mackinawite

Mackinawite
General
CategorySulfide mineral
Formula
(repeating unit)
(Fe,Ni)
1+x
S
(where x=0 to 0.11)
IMA symbolMkw[1]
Strunz classification2.CC.25
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupP4/nmm
Unit cella = 3.67 Å, c = 5.03 Å; Z = 2
Identification
Formula mass85.42 g/mol
ColorBronze to white grey
Crystal habitAs well-formed thin tabular crystals; massive, fine-feathery
CleavagePerfect on {001}
Mohs scale hardness2.5
LusterMetallic
StreakBlack
DiaphaneityOpaque
Specific gravity4.17
References[2][3][4][5]

Mackinawite is an iron nickel sulfide mineral with the chemical formula (Fe,Ni)
1+x
S
(where x = 0 to 0.11). The mineral crystallizes in the tetragonal crystal system and has been described as a distorted, close packed, cubic array of S atoms with some of the gaps filled with Fe.[6] Mackinawite 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. It was first described in 1962 for an occurrence in the Mackinaw mine, Snohomish County, Washington for which it was named.[5]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mineralienatlas
  3. ^ Handbook of Mineralogy
  4. ^ Webmineral data
  5. ^ a b Mindat
  6. ^ Taylor, L.A.; Finger, L.W. (1970). "Structural refinement and composition of mackinawite". Carnegie Institute of Washington Geophysical Laboratory Annual Report. 69: 318–322.