Meteoric iron

Meteoric iron, sometimes meteoritic iron,[1] is a native metal and early-universe protoplanetary-disk remnant found in meteorites and made from the elements iron and nickel mainly in the form of the mineral phases kamacite and taenite. Meteoric iron makes up the bulk of iron meteorites but is also found in other meteorites. Apart from minor amounts of telluric iron, meteoric iron is the only naturally occurring native metal of the element iron (in metallic form rather than in an ore) on the Earth's surface.[2]

Meteoric Iron (native iron)
Widmanstätten pattern on a 500g endcut from the Toluca iron meteorite
General
Category	Native element mineral
Formula (repeating unit)	Fe and Ni in different ratios
Space group	Different structures
Identification
Luster	Metallic
Diaphaneity	Opaque

Mineralogy

The bulk of meteoric iron consists of taenite and kamacite. Taenite is a face centered cubic and kamacite a body centered cubic iron-nickel-alloy.

Meteoric iron can be distinguished from telluric iron by its microstructure and perhaps by its chemical composition also, since meteoritic iron contains more nickel and less carbon.[2]

Trace amounts of gallium and germanium in meteoric iron can be used to distinguish different meteorite types. The meteoric iron in stony iron meteorites is identical to the "gallium-germanium group" of the iron meteorites.[3]

Overview over meteoric iron mineral phases

Mineral	Formula	Nickel (Mass-% Ni)	Crystal structure	Notes & references
Antitaenite	γLow Spin-(Ni,Fe)	20–40	face centered cubic	Only approved as a variety of taenite by the IMA
Kamacite	α-(Fe,Ni); Fe^0+0.9Ni0.1	5–10	body centered cubic	Same structure as ferrite
Taenite	γ-(Ni,Fe)	20–65	face centered cubic	Same structure as austenite
Tetrataenite	(FeNi)	48–57	tetragonal	[4]

Structures

Meteoric iron forms a few different structures that can be seen by etching or in thin sections of meteorites. The Widmanstätten pattern forms when meteoric iron cools and kamacite is exsolved from taenite in the form of lamellas.[5] Plessite is a more fine-grained intergrowth of the two minerals in between the lamella of the Widmanstätten pattern.[6] Neumann lines are fine lines running through kamacite crystals that form through impact-related deformation.[7]

Cultural and historical usage

A lance made from a narwhal tusk with an iron head made from the Cape York meteorite.

Before the advent of iron smelting, meteoric iron was the only source of iron metal apart from minor amounts of telluric iron. Meteoric iron was already used before the beginning of the Iron Age to make cultural objects, tools and weapons.[8]

Bronze Age

Many examples of iron working from the Bronze Age have been confirmed to be meteoritic in origin.[9]

• In ancient Egypt an iron metal bead was found in a graveyard near Gerzeh that contained 7.5% Ni.[10][11] Dated to around 3200 BC, geochemical analysis of the Gerzeh iron beads, based on the ratio of nickel to iron and cobalt, confirms that the iron was meteoritic in origin.[9]
• Dated to around 2500 BC, an iron dagger from Alaca Höyük was confirmed to be meteoritic in origin through geochemical analysis.[9]
• Dated to around 2300 BC, an iron pendant from Umm el-Marra in Syria was confirmed to be meteoritic in origin through geochemical analysis.[9]
• Dated to around 1400 BC, an iron axe from Ugarit in Syria was found to be meteoritic in origin.[9]
• Dated to around 1400 BC, several iron axes from the Shang Dynasty in China were also confirmed to be meteoritic in origin.[9]
• Dated to around 1350 BC, an iron dagger, bracelet and headrest from the tomb of Tutankhamun were confirmed to be meteoritic in origin.[9] The Tutankhamun dagger consists of similar proportions of metals (iron, nickel and cobalt) to a meteorite discovered in the area, deposited by an ancient meteor shower.[12][13][14]

The Americas

• The Inuit used parts of the Cape York meteorite to make lance heads.[15][16][17]

Africa

• Fragments from the Gibeon meteorite were used for centuries by the Nama people of Namibia.

Asia

• There are reports of the use of meteorites for manufacture of various items in Tibet (see Thokcha).
• The Iron Man, a statue of Vaiśravaṇa carved from an iron meteorite.,[18] a purported Tibetan Buddhist statue, the Iron Man, was likely carved from an ataxite meteorite. It has been speculated that it may be made from a fragment of the Chinga meteorite.[19][20]

Even after the invention of smelting, meteoric iron was sometimes used where this technology was not available or metal was scarce. A piece of the Cranbourne meteorite was made into a horseshoe around 1854.[21]

Today meteoritic iron is used in niche jewellery and knife production, but most of it is used for research, educational or collecting purposes.

Atmospheric phenomena

Meteoric iron also has an effect on the Earth's atmosphere. When meteorites descend through the atmosphere outer parts are ablated. Meteoric ablation is the source of many elements in the upper atmosphere. When meteoric iron is ablated it forms a free iron atom, that can react with ozone (O₃) to form FeO. This FeO may be the source of the orange spectrographic bands in the spectrum of the upper atmosphere.[22]

See also

• Glossary of meteoritics

References

1. Rehren, Thilo; Belgya, Tamás; Jambon, Albert; Káli, György; Kasztovszky, Zsolt; Kis, Zoltán; Kovács, Imre; Maróti, Boglárka; Martinón-Torres, Marcos; Miniaci, Gianluca; Pigott, Vincent C.; Radivojević, Miljana; Rosta, László; Szentmiklósi, László; Szőkefalvi-Nagy, Zoltán (2013). "5,000 years old Egyptian iron beads made from hammered meteoritic iron" (PDF). Journal of Archaeological Science. 40 (12): 4785–4792. doi:10.1016/j.jas.2013.06.002.
2. Fleming, Stuart J.; Schenck, Helen R. (1989). History of Technology: The Role of Metals. UPenn Museum of Archaeology. p. 67. ISBN 978-0-924171-95-6.
3. Lovering, John F.; Nichiporuk, Walter; Chodos, Arthur; Brown, Harrison (31 December 1956). "The distribution of gallium, germanium, cobalt, chromium, and copper in iron and stony-iron meteorites in relation to nickel content and structure". Geochimica et Cosmochimica Acta. 11 (4): 263–278. Bibcode:1957GeCoA..11..263L. doi:10.1016/0016-7037(57)90099-6.
4. Clarke, Roy S.; Edward R. D. Scott (1980). "Tetrataenite - ordered FeNi, a new mineral in meteorites" (PDF). American Mineralogist. 65: 624–630. Bibcode:1980AmMin..65..624C.
5. Yang, J.; J. I. Goldstein (2005). "The formation of the Widmanstätten structure in meteorites". Meteoritics & Planetary Science. 40 (2): 239–253. Bibcode:2005M&PS...40..239Y. doi:10.1111/j.1945-5100.2005.tb00378.x.
6. Goldstein, J. I.; J. R. Michael (2006). "The formation of plessite in meteoritic metal". Meteoritics & Planetary Science. 41 (4): 553–570. Bibcode:2006M&PS...41..553G. doi:10.1111/j.1945-5100.2006.tb00482.x.
7. Rosenhain, Walter; Jean McMinn (1925). "The Plastic Deformation of Iron and the Formation of Neumann Lines". Proceedings of the Royal Society. 108 (746): 231–239. Bibcode:1925RSPSA.108..231R. doi:10.1098/rspa.1925.0071.
8. Waldbaum, J. C. and James D. Muhly; The first archaeological appearance of iron and the transition to the iron age chapter in The coming of the age of iron, Theodore A. Wertme. ed., Yale University Press, 1980, ISBN 978-0300024258
9. Jambon, Albert (2017). "Bronze Age iron: Meteoritic or not? A chemical strategy" (PDF). Journal of Archaeological Science. 88: 47–53. doi:10.1016/j.jas.2017.09.008. ISSN 0305-4403.
10. "Pre-Dynastic Iron Beads from Gerzeh, Egypt". ucl.ac.uk. Archived from the original on 7 April 2015. Retrieved 28 December 2012.
11. Rehren, Thilo; Belgya, Tamás; Jambon, Albert; Káli, György; et al. (31 July 2013). "5,000 years old Egyptian iron beads made from hammered meteoritic iron". Journal of Archaeological Science. 40 (12): 4785–4792. doi:10.1016/j.jas.2013.06.002.
12. Bjorkman, Judith Kingston (1973). "Meteors and Meteorites in the ancient Near East". Meteoritics. 8 (2): 91–132. doi:10.1111/j.1945-5100.1973.tb00146.x.
13. Daniela Comelli; Massimo D'orazio; Luigi Folco; Mahmud El-Halwagy; Tommaso Frizzi; Roberto Alberti; Valentina Capogrosso; Abdelrazek Elnaggar; Hala Hassan; Austin Nevin; Franco Porcelli; Mohamed G. Rashed; Gianluca Valentini (2016). "The meteoritic origin of Tutankhamun's iron dagger blade". Meteoritics & Planetary Science. 51 (7): 1301–1309. Bibcode:2016M&PS...51.1301C. doi:10.1111/maps.12664.
14. Walsh, Declan (2 June 2016). "King Tut's Dagger Made of 'Iron From the Sky,' Researchers Say". The New York Times. Retrieved 4 June 2016. ...the blade's composition of iron, nickel and cobalt was an approximate match for a meteorite that landed in northern Egypt. The result "strongly suggests an extraterrestrial origin"
15. Iron and steel in ancient times by Vagn Fabritius Buchwald - Det Kongelige Danske Videnskabernes Selskab 2005
16. T. A. Rickard (1941). "The Use of Meteoric Iron". Journal of the Royal Anthropological Institute. 71 (1/2): 55–66. doi:10.2307/2844401. JSTOR 2844401.
17. Buchwald, V. F. (1992). "On the Use of Iron by the Eskimos in Greenland". Materials Characterization. 29 (2): 139–176. doi:10.1016/1044-5803(92)90112-U. JSTOR 2844401.
18. Der Lama mit der Hose: „Buddha from space“ ist offenbar eine Fälschung (Telepolis 13.10.2012)
19. "Ancient Buddhist Statue Made of Meteorite, New Study Reveals". Science Daily. Retrieved 26 December 2012.
20. Buchner, Elmar; Schmieder, Martin; Kurat, Gero; Brandstätter, Franz; et al. (1 September 2012). "Buddha from space-An ancient object of art made of a Chinga iron meteorite fragment*". Meteoritics & Planetary Science. 47 (9): 1491–1501. Bibcode:2012M&PS...47.1491B. doi:10.1111/j.1945-5100.2012.01409.x.
21. "The Cranbourne Meteorites" (PDF). City of Casey. Archived from the original (PDF) on 10 May 2013. Retrieved 29 December 2012.
22. Evans, W. F. J.; Gattinger, R. L.; Slanger, T. G.; Saran, D. V.; et al. (20 November 2010). "Discovery of the FeO orange bands in the terrestrial night airglow spectrum obtained with OSIRIS on the Odin spacecraft". Geophysical Research Letters. 37 (22): L22105. Bibcode:2010GeoRL..3722105E. doi:10.1029/2010GL045310.

External links

• Pictures of the iron beads of Gerzeh and other artifacts from tomb number 67