Greigite

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title: "Greigite" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["thiospinel-group", "iron(ii,iii)-minerals", "ferromagnetic-materials", "magnetic-minerals", "cubic-minerals", "minerals-in-space-group-227"] description: "Iron sulfide mineral of spinel structure" topic_path: "general/thiospinel-group" source: "https://en.wikipedia.org/wiki/Greigite" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Iron sulfide mineral of spinel structure ::

::data[format=table title="Infobox mineral"]

Field	Value
name	Greigite
image	Greigite structure 110 SFe4 tetrahedra.png
caption	Greigite structure, SFe4 tetrahedra
category	Sulfide mineral
Thiospinel group
Spinel structural group
formula
IMAsymbol	Grg
strunz	2.DA.05
system	Cubic
class	Hexoctahedral (mm)
H-M symbol: (4/m 2/m)
symmetry	Fdm
unit cell	a = 9.876 Å; Z = 8
color	Pale pink, tarnishes to metallic blue-black
habit	Spheres of intergrown octahedra and as disseminated microscopic grains
mohs	4 to 4.5
luster	Metallic to earthy
diaphaneity	Opaque
gravity	4.049
other	Strongly magnetic
references	{{cite book
volume	I (Elements, Sulfides, Sulfosalts)
::

| name = Greigite | image = Greigite structure 110 SFe4 tetrahedra.png | alt = | caption = Greigite structure, SFe4 tetrahedra | category = Sulfide mineral Thiospinel group Spinel structural group | formula = | IMAsymbol = Grg | molweight = | strunz = 2.DA.05 | dana = | system = Cubic | class = Hexoctahedral (mm) H-M symbol: (4/m 2/m) | symmetry = Fdm | unit cell = a = 9.876 Å; Z = 8 | color = Pale pink, tarnishes to metallic blue-black | colour = | habit = Spheres of intergrown octahedra and as disseminated microscopic grains | twinning = | cleavage = | fracture = | tenacity = | mohs = 4 to 4.5 | luster = Metallic to earthy | streak = | diaphaneity = Opaque | gravity = 4.049 | density = | polish = | opticalprop = | refractive = | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = Strongly magnetic | prop1 = | prop1text = | references = {{cite book|editor1=Anthony, John W. |editor2=Bideaux, Richard A. |editor3=Bladh, Kenneth W. |editor4=Nichols, Monte C. |title= Handbook of Mineralogy|publisher= Mineralogical Society of America|place= Chantilly, VA, US|chapter-url=http://rruff.geo.arizona.edu/doclib/hom/greigite.pdf |chapter=Greigite |access-date=December 5, 2011|isbn=0-9622097-0-8 |volume=I (Elements, Sulfides, Sulfosalts)|year=1990}} Greigite is an iron sulfide mineral with the chemical formula . It is the sulfur equivalent of the iron oxide magnetite (Fe3O4). It was first described in 1964 for an occurrence in San Bernardino County, California, and named after the mineralogist and physical chemist Joseph W. Greig (1895–1977).

Natural occurrence and composition

It occurs in lacustrine sediments with clays, silts and arkosic sand often in varved sulfide rich clays. It is also found in hydrothermal veins. Greigite is formed by magnetotactic bacteria and sulfate-reducing bacteria.

The mineral typically appears as microscopic (

Common impurities include Cu, Ni, Zn, Mn, Cr, Sb and As. In particular, the cubic Fe4S4 unit of greigite is found in the Fe4S4 thiocubane units of proteins of relevance to the acetyl-CoA pathway.

Crystal structure

Greigite has the spinel structure. The crystallographic unit cell is cubic, with space group Fd3m. The S anions form a cubic close-packed lattice, and the Fe cations occupy both tetrahedral and octahedral sites.

Magnetic and electronic properties

Like the related oxide magnetite (Fe3O4), greigite is ferrimagnetic, with the spin magnetic moments of the Fe cations in the tetrahedral sites oriented in the opposite direction as those in the octahedral sites, and a net magnetization. It is a mixed-valence compound, featuring both Fe(II) and Fe(III) centers in a 1:2 ratio. Both metal sites have high spin quantum numbers. The electronic structure of greigite is that of a half metal.

On Mars

A September 10, 2025 paper published in Nature reported the "likely" detection of greigite and vivianite in the Jezero crater on Mars, by the Perseverance rover. It is considered a potential biosignature.

References

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. [http://www.mindat.org/min-1747.html Greigite]. Mindat.org
3. [http://webmineral.com/data/Greigite.shtml Greigite]. Webmineral
4. (1964). "Greigite, the thio-spinel of iron; a new mineral". American Mineralogist.
5. "Armor-Plated Snail Discovered in Deep Sea".
6. (2004). "The rocky roots of the acetyl-CoA pathway". Trends in Biochemical Sciences.
7. (2009). "Electronic and magnetic structure of Fe₃S₄: GGA+U investigation". Physical Review B.
8. (2011). "The Curie temperature and magnetic exchange energy in half-metallic greigite Fe₃S₄". Physica Scripta.
9. (11 September 2025). "Redox-driven mineral and organic associations in Jezero Crater, Mars". Nature.
10. (2025-09-10). "NASA Says Mars Rover Discovered Potential Biosignature Last Year". NASA.

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