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The Mineralogy of Iron

General Properties
Symbol:Fe
Atomic Number:26
Standard atomic weight (Ar):55.845(2)
Electron configuration:[Ar] 3d6 4s2
Photos
<
Iron electrolytic and 1cm³ cube
>
Atomic Properties
Electronegativity (Pauling scale):1.83
Atomic Radius:156 pm
Ionic Radius:78 pm (+2*)
1st Ionization energy:763 kJ/mol
1st Electron affinity:-16 kJ/mol
Oxidation States:-2,-1,1,2,3,4,5,6
Physical Properties
Standard State:solid
Bonding Type:metallic
Melting Point:1811 K
Boiling Point:3134 K
Density:7.87 g/cm3
Metal/Non-Metal:transition metal
Main isotopes of Iron
Isotope% in NatureHalf LifeDecay typeDecay product
54Fe5.8%>3.1x1022yβ+β+ ?54Cr
55Fesynthetic2.73yε55Mn
56Fe91.72stable
57Fe2.2%Stable
58Fe0.28%stable
59Fesynthetic44.503dβ−59Co
60Fesynthetic2.6x106yβ−60Co
Main ions of Iron
NameIonExample minerals
Iron(II) (Ferrous)Fe2+Siderite
Iron(III) (Ferric)Fe3+Hematite, Goethite
Other Information
Year Discovered:Ancient
Named For:From the Anglo-Saxon: "holy metal", "strong metal"
CPK color coding:#E06633
External Links:WikipediaWebElementsLos Alamos National LaboratoryTheodore Gray's PeriodicTable.com
Simple Compounds and Mineral Names
Nitridesdiiron nitrideFe2N
tetrairon nitrideFe4NRoaldite
Sulfidesiron (II) sulfideFeS+2Troilite, Pyrrhotite
iron persulfideFeS2+2Pyrite, Marcasite
triiron tetrasulfideFe3S4+2,+3Greigite
Selenidesiron selenideFeSe+2
iron perselenideFeSe2+2Ferroselite, Dzharkenite
Telluridesiron tellurideFeTe+2
iron pertellurideFeTe2+2Frohbergite
Hydroxidesiron (II) hydroxideFe(OH)2+2
iron (III) hydroxideFe(OH)3+3Bernalite
iron (III) oxide-hydroxideFeO(OH)+3Goethite, Akaganeite, Lepidocrocite, Feroxyhyte
Fluoridesiron (II) fluorideFeF2+2
iron (III) fluorideFeF3+3
Chloridesiron (II) chlorideFeCl2+2Lawrencite
iron (III) chlorideFeCl3+3Molysite
iron (II) chloride dihydrateFeCl2 · 2H2O+2Rokühnite
Bromidesiron (II) bromide FeBr2
iron (III) bromide FeBr3
IodidesIron (II) diiodide FeI2
Iron (III) iodide FeI3
Oxidesiron (II) oxideFeO+2
iron (iii) oxideFe2O3+3Hematite
triiron tetraoixdeFe3O4+2,+3Magnetite
Carbonatesiron (II) carbonateFeCO3+2Siderite
iron (III) carbonateFe2(CO3)3+3
Nitratesiron (II) nitrateFe(NO3)2+2
iron (III) nitrateFe(NO3)3+3
iron (III) nitrate nonahydrateFe(NO3)3 · 9H2O+3
Sulfatesiron (II) sulfateFeSO4+2
iron (III) sulfateFe2(SO4)3+3Mikasaite
iron (II) sulfate hydrateFeSO4 · H2O+2Szomolnokite
iron (II) sulfate tetrahydrateFeSO4 · 4H2O+2Rozenite
iron (II) sulfate pentahydrateFeSO4 · 5H2O+2Siderotil
iron (II) sulfate hexahydrateFeSO4 · 6H2O+2Ferrohexahydrite
iron (II) sulfate heptahydrateFeSO4 · 7H2O+2Melanterite
iron (III) sulfate pentahydrateFe2(SO4)3 · 5H2O+3Lausenite
iron (III) sulfate heptahydrateFe2(SO4)3 · 7H2O+3Kornelite
iron (III) sulfate nonahydrateFe2(SO4)3 · 9H2O+3Paracoquimbite
iron (III) sulfate undecahydrateFe2(SO4)3 · 11H2O+3Quenstedtite
Iron as a chromophore in minerals and gems
ChromophoreDescription
Fe2+Green colour, eg in forsterite (peridot) and the blue-green colour in phosphophyllite. In some minerals with high concentrations of Fe2+ the colour is brown.
Fe2+ in square planar siteRaspberry red colour in gillespite from El Roasrio, Baja California, Mexico.
Fe2+ in eight-coordinate siteHigher concentrations in pyrope garnet cause a deeper red colour.
Fe3+ in octahedral sitesWhen the Fe3+ ions are isolated by intervening ions it leads to a pale colour, such as the pale purple colour in strengite and coquimbite. Also the yellow-green colour in ferric silicates such as andradite.
Fe3+ in tetrahedral sitesCauses the pale yellow colour in a plagioclase feldspar from Lake County, Oregon.
Fe4+ in deformed tetrahedral silicon positionThe colour in amethyst has been explained as Fe3+ replacing Silicon losing an electron due to radioactive bombardment to become tetravalent Fe4+.
Fe2+ - Fe3+ IVCTIntervalence Charge Transfer between two adjacent metal ions. Usually causes blue-green coloration, examples include rockbridgeite and vivianite.
Fe2+ - Ti4+ IVCTbrown to brownish-red colouration eg in dravite and neptunite (where the reddish tint is more noticeable in thin section.
Mineral Diversity of Iron
1. Elements 34 valid mineral species
2. Sulfides And Sulfosalts 96 valid mineral species
3. Halides11 valid mineral species
4. Oxides 110 valid mineral species
5. Carbonates 10 valid mineral species
6. Borates10 valid mineral species
7. Sulfates 90 valid mineral species
8. Phosphates, Arsenates, Vanadates230 valid mineral species
9. Silicates 247 valid mineral species
10. Organic Compounds3 valid mineral species
Total:841 valid species containing essential Iron
Geochemistry of Iron
Goldschmidt classification:Siderophile
Fe2+ was one of the ions least depleted from the mantle in the formation of the crust.
Fe3+ enters early-forming phases in igneous rocks.
Fe2+ enters early-forming phases in igneous rocks.
Fe3+ is commonly concentrated in residual soils and sediments.
Fe3+ is concentrated in deep-sea ferromanganese nodules relative to seawater.
Fe2+ solute can be a limiting nutrient in the growth of bacteria.
Fe2+ solute can be a limiting nutrient in the oceans.
Fe2+ solute is a micronutrient on land.
Fe2+ is essential to nutrition of at least some vertebrates ('essential minerals').
Elemental Iron in Nature
Found as native element:IronFe
Taenite(Fe,Ni)
Found as natural alloy with Cu:TulameenitePt2CuFe
Found as natural alloy with Pt:IsoferroplatinumPt3Fe
TetraferroplatinumPtFe
Elemental Abundance for Iron
Crust (CRC Handbook)5.63 x 10-2mass fraction, kg/kg
Crust (Kaye & Laby)5.8 x 10-2mass fraction, kg/kg
Crust (Greenwood)6.2000 x 10-2mass fraction, kg/kg
Crust (Ahrens/Taylor)7.07 x 10-2mass fraction, kg/kg
Crust (Ahrens/Wänke)4.92 x 10-2mass fraction, kg/kg
Crust (Ahrens/Weaver)3.8 x 10-2mass fraction, kg/kg
Upper Crust (Ahrens/Taylor)3.50 x 10-2mass fraction, kg/kg
Upper Crust (Ahrens/Shaw)3.09 x 10-2mass fraction, kg/kg
Sea Water (CRC Handbook)2 x 10-9mass per volume fraction, kg/L
Sea Water (Kaye & Laby)3.4 x 10-9mass per volume fraction, kg/L
The Sun (Kaye & Laby)9.0 x 10-1atom mole fraction relative to Si=1
Solar System (Kaye & Laby)9.0 x 10-1atom mole fraction relative to Si=1
Solar System (Ahrens)9.00 x 10-1 (2.7%)atom mole fraction relative to Si=1 (% uncertainty)
Element association of Iron in the Mineral World
This table compares the known valid mineral species listed listed with Iron and the other elements listed based on the official IMA formula. Note that unlike other sections on this page this includes non-essential elements.

The first data column contains the total number of minerals listed with Iron and the element listed for that row.

The second data column lists this number as a percentage of all minerals listed with Iron.

The final data column compares this percentage against the percentage of all minerals that contain the element listed in each row.

Click on a heading to sort.
ElementValid Minerals listed with element and Iron% of Fe mineralsRelative to % in all minerals
Oxygen3092 minerals with Fe and O85.51%6.66% higher
Hydrogen2172 minerals with Fe and H60.07%7.43% higher
Silicon1173 minerals with Fe and Si32.44%14.68% higher
Calcium876 minerals with Fe and Ca24.23%0.97% lower
Aluminium788 minerals with Fe and Al21.79%8.30% higher
Sodium756 minerals with Fe and Na20.91%9.09% higher
Magnesium737 minerals with Fe and Mg20.38%54.34% higher
Sulfur723 minerals with Fe and S19.99%4.47% lower
Phosphorus661 minerals with Fe and P18.28%55.78% higher
Manganese581 minerals with Fe and Mn16.07%45.11% higher
Titanium458 minerals with Fe and Ti12.67%84.62% higher
Arsenic402 minerals with Fe and As11.12%9.24% lower
Potassium371 minerals with Fe and K10.26%9.17% higher
Copper355 minerals with Fe and Cu9.82%25.24% lower
Zinc252 minerals with Fe and Zn6.97%33.42% higher
Lead246 minerals with Fe and Pb6.80%33.47% lower
Fluorine223 minerals with Fe and F6.17%20.92% lower
Chlorine185 minerals with Fe and Cl5.12%30.98% lower
Barium180 minerals with Fe and Ba4.98%8.69% higher
Nickel157 minerals with Fe and Ni4.34%40.51% higher
Niobium140 minerals with Fe and Nb3.87%30.75% higher
Boron139 minerals with Fe and B3.84%26.15% lower
Cerium123 minerals with Fe and Ce3.40%15.59% higher
Zirconium120 minerals with Fe and Zr3.32%44.35% higher
Antimony113 minerals with Fe and Sb3.13%36.60% lower
Vanadium110 minerals with Fe and V3.04%32.21% lower
Strontium97 minerals with Fe and Sr2.68%4.93% higher
Carbon96 minerals with Fe and C2.65%65.88% lower
Yttrium89 minerals with Fe and Y2.46%2.94% higher
Uranium83 minerals with Fe and U2.30%55.90% lower
Tin81 minerals with Fe and Sn2.24%25.56% higher
Chromium75 minerals with Fe and Cr2.07%16.26% higher
Lithium72 minerals with Fe and Li1.99%4.20% lower
Beryllium70 minerals with Fe and Be1.94%13.02% lower
Lanthanum68 minerals with Fe and La1.88%64.91% higher
Tellurium61 minerals with Fe and Te1.69%46.36% lower
Bismuth61 minerals with Fe and Bi1.69%60.47% lower
Molybdenum59 minerals with Fe and Mo1.63%30.46% higher
Nitrogen53 minerals with Fe and N1.47%32.47% lower
Silver53 minerals with Fe and Ag1.47%57.38% lower
Tantalum51 minerals with Fe and Ta1.41%17.97% higher
Cobalt45 minerals with Fe and Co1.24%3.34% lower
Germanium45 minerals with Fe and Ge1.24%105.04% higher
Tungsten35 minerals with Fe and W0.97%16.95% higher
Thorium31 minerals with Fe and Th0.86%19.52% higher
Thallium30 minerals with Fe and Tl0.83%37.35% lower
Selenium27 minerals with Fe and Se0.75%68.28% lower
Platinum21 minerals with Fe and Pt0.58%9.78% lower
Iridium20 minerals with Fe and Ir0.55%50.36% higher
Neodymium17 minerals with Fe and Nd0.47%20.12% lower
Indium12 minerals with Fe and In0.33%28.88% higher
Caesium12 minerals with Fe and Cs0.33%27.83% lower
Rhodium8 minerals with Fe and Rh0.22%29.24% lower
Scandium7 minerals with Fe and Sc0.19%44.60% lower
Cadmium7 minerals with Fe and Cd0.19%61.02% lower
Osmium6 minerals with Fe and Os0.17%12.77% higher
Mercury6 minerals with Fe and Hg0.17%90.89% lower
Ruthenium6 minerals with Fe and Ru0.17%24.82% lower
Gallium5 minerals with Fe and Ga0.14%7.40% higher
Gold3 minerals with Fe and Au0.08%86.33% lower
Rhenium3 minerals with Fe and Re0.08%125.54% higher
Ytterbium1 mineral with Fe and Yb0.03%62.41% lower
Palladium1 mineral with Fe and Pd0.03%97.88% lower
Periodic Table
1H 2He
3Li 4Be 5B 6C 7N 8O 9F 10Ne
11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar
19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr
37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe
55Cs 56Ba 57La 72Hf 73Ta 74W 75Re 76Os 77Ir 78Pt 79Au 80Hg 81Tl 82Pb 83Bi 84Po 85At 86Rn
87Fr 88Ra 89Ac 104Rd 105Db 106Sg 107Bh 108Hs 109Mt 110Ds 111Rg 112Cn 113Nh 114Fl 115Mc 116Lv 117Ts 118Og
 
58Ce 59Pr 60Nd 61Pm 62Sm 63Eu 64Gd 65Tb 66Dy 67Ho 68Er 69Tm 70Yb 71Lu
90Th 91Pa 92U 93Np 94Pu 95Am 96Cm 97Bk 98Cf 99Es 100Fm 101Md 102No 103Lr
Default Categories CPK Electronegativity Atomic Radius Lowest Oxidation Highest Oxidation Crustal Abundance Goldschmidt Mineral Species Minerals with Fe Relative Frequency
Manganese << Iron >> Cobalt


Most widespread minerals containing Iron
This list of minerals containing Iron is built from the mindat.org locality database. This is based on the number of localities entered for mineral species and is therefore slanted towards minerals interesting to collectors with less coverage of common rock-forming-minerals so it does not give an undistorted distribution of Iron mineral species. It is more useful when comparing rare species rather than common species.
NameFormulaCrystal SystemMindat Localities
PyriteFeS2Isometric35796
ChalcopyriteCuFeS2Tetragonal25003
MagnetiteFe2+Fe3+2O4Isometric14879
Photos

Localities with greatest number of different Iron mineral species
map should go here
4Hagendorf South Pegmatite (Cornelia Shaft; Hagendorf South Open Cut), Hagendorf, Waidhaus, Upper Palatinate, Bavaria, Germany79 Fe minerals
3Clara Mine, Rankach valley, Oberwolfach, Wolfach, Ortenaukreis, Baden-Württemberg, Germany87 Fe minerals
6Poudrette quarry (De-Mix quarry; Demix quarry; Uni-Mix quarry; Carrière Mont Saint-Hilaire; MSH), Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada72 Fe minerals
8Palermo No. 1 Mine (Palermo No. 1 pegmatite; Hartford Mine; GE Mine), Groton, Grafton Co., New Hampshire, USA67 Fe minerals


Important ores of Iron
NameFormulaCrystal System
HematiteFe2O3Trigonal
Goethiteα-Fe3+O(OH)Orthorhombic
Limonite(Fe,O,OH,H2O)
Photos


Minor ores of Iron
NameFormulaCrystal System
SideriteFeCO3Trigonal
PyriteFeS2Isometric
Photos


Spotted a mistake/omission? - These pages are a work in progress, so please send all comments/corrections to jolyon@mindat.org. Thank you.

Constants and physical property data from:

David R. Lide (ed.), CRC Handbook of Chemistry and Physics, 85th Edition. CRC Press. Boca Raton, Florida (2005).
Kaye and Laby Tables of Physical & Chemical Constants (2005). Section 3.1.3, Abundances of the elements
A. Earnshaw, N. Greenwood, Chemistry of the Elements, 2nd edition, Butterworth-Heinemann, (1997)
Thomas J. Ahrens (ed.), Global Earth Physics : A Handbook of Physical Constants, American Geophysical Union (1995)
L.B. Railsback, An Earth Scientist's Periodic Table of the Elements and Their Ions : Geology 31:9 p737-740 (2003)
Emsley, J. Nature's Building Blocks: An A-Z Guide to the Elements. New York: Oxford University Press (2001)
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