Meteoric iron, sometimes meteoritic iron, is a

native metal A native metal is any metal that is found pure in its metallic form in nature. Metals that can be found as native element mineral, native deposits singly or in alloys include antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, ma ...

and early-universe protoplanetary-disk remnant found in meteorites and made from the elements

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

and nickel, mainly in the form of the

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

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.

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 An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

. 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. Trace amounts of

gallium Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, elemental gallium is a soft, silvery metal at standard temperature and pressure. ...

and

germanium Germanium is a chemical element; it has Symbol (chemistry), symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically ...

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.

Structures

Meteoric iron forms a few different structures that can be seen by

etching Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio (incised) in the metal. In modern manufacturing, other chemicals may be used on other type ...

or in thin sections of meteorites. The

Widmanstätten pattern Widmanstätten patterns (), also known as Thomson structures, are figures of long Phase (matter), phases of nickel–iron, found in the octahedrite shapes of iron meteorite crystals and some pallasites. Iron meteorites are very often formed ...

forms when meteoric iron cools and kamacite is exsolved from taenite in the form of lamellas. Plessite is a more fine-grained intergrowth of the two minerals in between the lamella of the Widmanstätten pattern. Neumann lines are fine lines running through kamacite crystals that form through impact-related deformation.

Cultural and historical usage

Before the advent of iron

smelting Smelting is a process of applying heat and a chemical reducing agent to an ore to extract a desired base metal product. It is a form of extractive metallurgy that is used to obtain many metals such as iron-making, iron, copper extraction, copper ...

, 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 The Iron Age () is the final epoch of the three historical Metal Ages, after the Chalcolithic and Bronze Age. It has also been considered as the final age of the three-age division starting with prehistory (before recorded history) and progre ...

to make cultural objects, tools and weapons.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,

Bronze Age

Many examples of iron working from the

Bronze Age The Bronze Age () was a historical period characterised principally by the use of bronze tools and the development of complex urban societies, as well as the adoption of writing in some areas. The Bronze Age is the middle principal period of ...

have been confirmed to be meteoritic in origin. *In ancient Egypt an iron metal bead was found in a graveyard near Gerzeh that contained 7.5% Ni. Dated to around 3200 BC,

geochemical Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the ...

analysis of the Gerzeh iron beads, based on the ratio of nickel to iron and

cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...

, confirms that the iron was meteoritic in origin. *In

Mesopotamia Mesopotamia is a historical region of West Asia situated within the Tigris–Euphrates river system, in the northern part of the Fertile Crescent. Today, Mesopotamia is known as present-day Iraq and forms the eastern geographic boundary of ...

Sumer Sumer () is the earliest known civilization, located in the historical region of southern Mesopotamia (now south-central Iraq), emerging during the Chalcolithic and Early Bronze Age, early Bronze Ages between the sixth and fifth millennium BC. ...

and

Akkadian Empire The Akkadian Empire () was the first known empire, succeeding the long-lived city-states of Sumer. Centered on the city of Akkad (city), Akkad ( or ) and its surrounding region, the empire united Akkadian language, Akkadian and Sumerian languag ...

, meteoric iron was considered a sacred material, used to create special ritual objects, and used long before the systematic processing of terrestrial iron. There was a special term for it, an-bar. *Dated to around 2500 BC, an iron dagger from Alaca Höyük was confirmed to be meteoritic in origin through geochemical analysis. *Dated to around 2300 BC, an iron pendant from Umm el-Marra in Syria was confirmed to be meteoritic in origin through geochemical analysis. *Dated to around 1400 BC, an iron axe from Ugarit in Syria was found to be meteoritic in origin. *Dated to around 1400 BC, several iron axes from

Shang dynasty The Shang dynasty (), also known as the Yin dynasty (), was a Chinese royal dynasty that ruled in the Yellow River valley during the second millennium BC, traditionally succeeding the Xia dynasty and followed by the Western Zhou d ...

China were confirmed to be meteoritic in origin. *Dated to around 1350 BC, an iron dagger, bracelet and headrest from the tomb of

Tutankhamun Tutankhamun or Tutankhamen, (; ), was an Egyptian pharaoh who ruled during the late Eighteenth Dynasty of Egypt, Eighteenth Dynasty of ancient Egypt. Born Tutankhaten, he instituted the restoration of the traditional polytheistic form of an ...

were confirmed to be meteoritic in origin. The Tutankhamun dagger consists of similar proportions of metals (

, nickel and

) to a meteorite discovered in the area, deposited by an ancient meteor shower. *Dated to around 900 BC, an

arrowhead An arrowhead or point is the usually sharpened and hardened tip of an arrow, which contributes a majority of the projectile mass and is responsible for impacting and penetrating a target, or sometimes for special purposes such as signaling. ...

from Mörigen in Switzerland was confirmed to be made of meteoric iron whose composition suggested that it originated from the Kaali meteorite crater in Saaremaa, Estonia.

The Americas

*The

Inuit Inuit (singular: Inuk) are a group of culturally and historically similar Indigenous peoples traditionally inhabiting the Arctic and Subarctic regions of North America and Russia, including Greenland, Labrador, Quebec, Nunavut, the Northwe ...

used parts of the

Cape York meteorite The Cape York meteorite, also known as the Innaanganeq meteorite, is one of the largest known iron meteorites, classified as a medium octahedrite in chemical group IIIAB meteorites, IIIAB. In addition to many small fragments, at least eight large ...

to make knives, harpoon tips, lance heads. Large quantities of meteoric iron were known and used long before European contact.

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 purported Tibetan Buddhist statue of Vaiśravaṇa, was likely carved from an ataxite meteorite.Der Lama mit der Hose: „Buddha from space“ ist offenbar eine Fälschung (Telepolis 13.10.2012)
/ref> It has been speculated that it may be made from a fragment of the Chinga meteorite. Even after the invention of

, meteoric iron was sometimes used where this technology was not available or metal was scarce. A piece of the

Cranbourne meteorite The Cranbourne meteorite is an octahedrite iron meteorite. It is the second largest meteorite found in Australia after the Mundrabilla meteorite, but at the time of discovery it was the largest known iron meteorite in the world. It is classifi ...

was made into a horseshoe around 1854. 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 Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...

(O₃) to form FeO. This FeO may be the source of the orange spectrographic bands in the spectrum of the upper atmosphere.

References

External links

Pictures of the iron beads of Gerzeh and other artifacts from tomb number 67
{{Meteorites Iron Meteorite minerals Native element minerals