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Cohenite
A valid IMA mineral species - grandfathered
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About Cohenite
Emil Cohen
Formula:
Fe3C
May contain minor Ni or Co replacing Fe.
Colour:
Tin white
Lustre:
Metallic
Hardness:
5½ - 6
Specific Gravity:
7.20 - 7.65
Crystal System:
Orthorhombic
Name:
In honor of Emil Wilhelm Cohen (12 October 1842, Akjär, Jutland, Denmark- 13 April 13, 1905, Greifswald, Germany), Professor of Mineralogy, University of Greifswald, Greifswald, Germany. He was a founder of modern petrography and was among the first to study the petrography of iron meteorites.
In technical iron alloys, cohenite is well-known as a synthetic phase and is called cementite (Zementit in German).
See also austenite.
See also austenite.
Unique Identifiers
Mindat ID:
1107
Long-form identifier:
mindat:1:1:1107:1
Similar Names
IMA Classification of Cohenite
Approved, 'Grandfathered' (first described prior to 1959)
First published:
1889
Classification of Cohenite
1.BA.05
1 : ELEMENTS (Metals and intermetallic alloys; metalloids and nonmetals; carbides, silicides, nitrides, phosphides)
B : Metallic Carbides, Silicides, Nitrides, Phosphides and Hydrides
A : Carbides
1 : ELEMENTS (Metals and intermetallic alloys; metalloids and nonmetals; carbides, silicides, nitrides, phosphides)
B : Metallic Carbides, Silicides, Nitrides, Phosphides and Hydrides
A : Carbides
Dana 7th ed.:
1.1.24.1
1.1.16.1
1 : NATIVE ELEMENTS AND ALLOYS
1 : Metals, other than the Platinum Group
1 : NATIVE ELEMENTS AND ALLOYS
1 : Metals, other than the Platinum Group
2.11
2 : Carbides, Nitrides, Silicides and Phosphides
2 : Carbides, Nitrides, Silicides and Phosphides
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Coh | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Coh | Whitney & Evans (2010) | Whitney, D.L. and Evans, B.W. (2010) Abbreviations for names of rock-forming minerals. American Mineralogist, 95, 185–187 doi:10.2138/am.2010.3371 |
Physical Properties of Cohenite
Metallic
Transparency:
Opaque
Colour:
Tin white
Comment:
Tin-white; oxidizes to light bronze then golden yellow.
Hardness:
5½ - 6 on Mohs scale
Tenacity:
Very brittle
Cleavage:
Distinct/Good
{100}, {010}, and {001}.
{100}, {010}, and {001}.
Density:
7.20 - 7.65 g/cm3 (Measured) 7.68 g/cm3 (Calculated)
Optical Data of Cohenite
Type:
Biaxial
Reflectivity:
| Wavelength | R1 (%) | R2 (%) |
|---|---|---|
| 400nm | 51.8% | 54.7% |
| 420nm | 52.6% | 55.2% |
| 440nm | 53.2% | 55.7% |
| 460nm | 53.8% | 56.2% |
| 480nm | 54.4% | 56.7% |
| 500nm | 55.0% | 57.1% |
| 520nm | 55.6% | 57.7% |
| 540nm | 56.2% | 58.2% |
| 560nm | 56.8% | 58.8% |
| 580nm | 57.4% | 59.3% |
| 600nm | 58.0% | 60.0% |
| 620nm | 58.7% | 60.6% |
| 640nm | 59.3% | 61.3% |
| 660nm | 60.0% | 62.0% |
| 680nm | 60.8% | 62.8% |
| 700nm | 61.6% | 63.6% |
Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 63.6%.
R1 shown in black, R2 shown in red
Chemistry of Cohenite
Mindat Formula:
Fe3C
May contain minor Ni or Co replacing Fe.
May contain minor Ni or Co replacing Fe.
Elements listed:
Crystallography of Cohenite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Cell Parameters:
a = 5.09 Å, b = 6.74 Å, c = 4.52 Å
Ratio:
a:b:c = 0.755 : 1 : 0.671
Unit Cell V:
155.07 ų (Calculated from Unit Cell)
Z:
4
Comment:
Space Group: P bnm.
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0013522 | Cohenite | Fruchart D, Chaudouet P, Fruchart R, Rouault A, Senateur J P (1984) Etudes structurales de composes de type cementite: effet de l'hydrogene sur Fe3C suivi par diffraction neutronique. Spectrometrie Mossbauer sur FeCo2B et Co3B dopes au 57Fe Journal of Solid State Chemistry 51 246-252 | 1984 | synthetic | 0 | 293 | |
| 0019097 | Cohenite | Herbstein F H, Smuts J (1964) Comparison of X-ray and neutron-diffraction refinements of the structure of cementite Fe3C Acta Crystallographica 17 1331-1332 |  | 1964 | synthetic | 0 | 293 |
| 0019132 | Cohenite | Lyashchenko B G, Sorokin L M (1963) Determination of the position of carbon in cementite by the neutron diffraction method Soviet Physics Crystallography 8 300-304 | 1963 | synthetic | 0 | 293 | |
| 0019094 | Cohenite | Meinhardt D, Krisement O (1962) Strukturuntersuchungen an Karbiden des Eisens, Wolframs und Chroms mit thermischen Neutronen Archiv fur das Eisenhuettenwesen 33 493-499 | 1962 | synthetic | 0 | 293 | |
| 0019095 | Cohenite | Lipson H, Petch N J (1940) The crystal structure of cementite, Fe3C The Journal of the Iron and Steel Institute (London) 142 95-103 | 1940 | synthetic | 0 | 293 | |
| 0017653 | Cohenite | Shimura S (1930) A study on the structure of cementite _cod_database_code 1010931 Proceedings of the Japan Academy 6 269-271 | 1930 | synthetic | 0 | 293 | |
| 0017653 | Cohenite | Shimura S (1930) A study on the structure of cementite _cod_database_code 1010931 Proceedings of the Japan Academy 6 269-271 | 1930 | synthetic | 0 | 293 | |
| 0010504 | Cohenite | Hendricks B S (1930) The crystal structure of cementite Zeitschrift fur Kristallographie 74 534-545 |  | 1930 | synthetic | 0 | 293 |
| 0019113 | Cohenite | Wood I G, Vocadlo L, Knight K S, Dobson D P, Marshall W G, Price G D, Brodholt J (2004) Thermal expansion and crystal structure of cementite, Fe3C, between 4 and 600 K determined by time-of-flight neutron powder diffraction Journal of Applied Crystallography 37 82-90 | 2004 | synthetic | 0 | 300 | |
| 0019112 | Cohenite | Wood I G, Vocadlo L, Knight K S, Dobson D P, Marshall W G, Price G D, Brodholt J (2004) Thermal expansion and crystal structure of cementite, Fe3C, between 4 and 600 K determined by time-of-flight neutron powder diffraction Journal of Applied Crystallography 37 82-90 | 2004 | synthetic | 0 | 280 | |
Maimechinskaya intrusion, Maimecha and Kotui Rivers Basin, Krasnoyarsk Krai, Russia