Radiation astronomy/Alloys

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The "Swarm" satellites have been flying around Earth since Fall of 2013. Credit: Christoph Seidler, ESA/DTU.{{fairuse}}
Depiction shows where the molten iron jet is moving - in the outer core. Credit: ESA.{{fairuse}}

"Three [Swarm] satellites of the European Space Agency (ESA) have measured the magnetic field of Earth more precisely than ever before."[1]

A "kind of "jet stream" - a fast-flowing river of liquid iron [depicted with an artist's impression in the image on the left] is surging westwards under Alaska and Siberia."[2]

"The moving mass of metal has been inferred from measurements made by Europe’s Swarm satellites. [...] the jet is the best explanation for the patches of concentrated field strength that the satellites observe in the northern hemisphere."[2]

Earth cores[edit | edit source]

"The core was the first internal structural element to be identified. It was discovered in 1906 by R.D. Oldham, from his study of earthquake records, and it helped to explain Newton's calculation of the Earth's density. The outer core is presumed to be liquid because it does not transmit shear (S) waves and because the velocity of compressional (P) waves that pass through it is sharply reduced. The inner core is considered to be solid because of the behavior of P and S waves passing through it."[3]

"Data from [seismic] waves, rotations and inertia of the whole Earth, magnetic-field dynamo theory, and laboratory experiments on melting and alloying of iron all contribute to the identification of the composition of the inner and outer core. The core is presumed to be composed principally of iron, with about 10 percent alloy of oxygen or sulfur or nickel, or perhaps some combination of these three elements."[3]

Outer cores[edit | edit source]

"This jet of liquid iron is moving at about fifty kilometres per year. That might not sound like a lot to you on Earth's surface, but you have to remember this a very dense liquid metal and it takes a huge amount of energy to move this thing around and that's probably the fastest motion we have anywhere within the solid Earth.”[4]

The "jet [is] about 420 km wide, and [...] wraps half-way around the planet."[2]

“It's likely that the jet stream has been in play for hundreds of millions of years."[5]

"It currently wraps about 180 degrees around the tangent cylinder [a boundary between two different regions in the core, a tube sitting around the solid inner core, running along Earth’s rotation axis]. Although observations only constrain the jet stream on the edge of the core, our theoretical understanding suggests that the jet could in principle go very deep indeed - possibly in fact all the way down to the edge of the core in the southern hemisphere (i.e. at the other end of the tangent cylinder)."[5]

"When liquid iron approaches the boundary from both sides, it gets squeezed out sideways to form the jet, which then hugs the imaginary tube."[2]

"Of course, you need a force to move fluid towards the tangent cylinder. This could be provided by buoyancy, or perhaps more likely from changes in the magnetic field within the core."[6]

Inner cores[edit | edit source]

Artist's impression depicts the inner core scaled outward. Credit: BBC Science Photo Library.{{fairuse}}

We know that the Earth's core is composed of an alloy of iron and other minerals.[7]

"A PKJKP [P wave, traversing the outer core K, and the inner core J, to emerge again as the P wave] traverses the inner core as a shear wave, so this is the direct evidence that the inner core is solid, because only in the solid material the shear wave can exist. In the liquid material, say water, only the compressional wave can travel through."[8]

Studying "archived data from about 20 large earthquakes, all monitored by an array of German seismic detectors back in the 1980s and '90s" has "reliably detected" a PKJKP wave in 2005, demonstrating that the inner core is solid.[9]

The inner core, however, is solid because of the enormous pressure.[10]

The inner core "is a solid ball of superhot iron and nickel alloy about 760 miles (1,220 kilometers) in diameter. ... the inner core is, at 10,800 degrees Fahrenheit (6,000 degrees Celsius), as hot as the surface of the sun."[11]

"We know the Earth's inner core is composed mostly of iron".[12]

"The metal [iron] was subjected to more than 200 billion pascals of pressure".[11]

"[M]aterial within Earth's inner core is apparently distributed in a lopsided way ... The weakness of iron might lead crystallites in the inner core to flow and line up a certain way".[11]

"[T]he speed at which the inner core spun apparently fluctuated over the course of approximately decades between 1961 and 2007."[11]

"As the inner core cools, crystallizing iron releases impurities, sending lighter molten material into the liquid outer core. This upwelling, combined with the Earth's rotation, drives convection, forcing the molten metal into whirling vortices. These vortices stretch and twist magnetic field lines, creating Earth’s magnetic field. Currently, the center of the field, called an axis, emerges in the Arctic Ocean west of Ellesmere Island, about 300 miles (500 kilometers) from the geographic North Pole."[13]

"In the last decade, seismic waves from earthquakes revealed the inner core looks like a navel orange, bulging slightly more on its western half. Geoscientists recently explained the asymmetry by proposing a convective loop: The inner core might be crystallizing on one half and melting on the other."[13]

"The lopsided growth of the inner core makes convection in the outer core a little bit lopsided, and that then induces the geomagnetic field to have this lopsided or eccentric character too".[14]

"Magnetic particles trapped and aligned in rocks reveal that the magnetic north pole wandered around the Western Hemisphere over the past 10,000 years, and circled the Eastern Hemisphere before that — a result mirrored by the numerical test."[13]

"The key question for interesting ideas like translational instability is, 'Can we test it?' ... What we're doing is proposing a test, and we think it's a good test because people can go out and look for eccentricity in the rock record and that will either confirm or shoot down this idea."[14]

"Within less than 100 million years, everything that has been crystallized on the west will have melted on the east".[15]

Seismic "waves appear to travel faster through the inner core from north to south than from west to east. Seismic properties also seemed to vary between the Eastern and Western hemispheres of the globe."[16]

There is a "124-mile (200-km) thick layer of dense material detected on its surface."[16]

"[T]he inner core [may be] shifted slightly off-center, just to the east. This would put more pressure on the western side, where it would be closer to the center of the planet, and less pressure on the eastern side. The result could be a perpetually denser Western hemisphere and a continual flow of dense fluid from the east that eventually spreads out atop the entire inner core."[16]

"The inner core is basically regenerating itself. And superimposed on that is this overall cooling that makes the inner core bigger and bigger over time".[17]

"It is the first observational evidence that the inner core rotates at a variety of speeds with respect to the mantle...It also reconciles old discrepancies".[18]

"The inner core, on average, rotates eastward. At the speeds it travels, it might, on average, complete a revolution every 750 to 1,440 years. However, these speeds appear unstable, which makes it uncertain just how long it actually takes to finish a turn on its axis".[11]

"Earth’s magnetic field [...] is powered by circulation of iron-rich fluid in the core. [...] Earth’s solid inner core [may have] formed after 565 million years ago, saving a weakening magnetic field from collapse."[19]

"We don’t have many real benchmarks for the thermal history of our planet."[20]

"We know the interior was hotter than today, because all planets lose heat. But we don’t know what the average temperature was a billion years ago, compared with today. Pinning down when iron in the inner core began to crystallize could offer a window into how hot the interior of the planet was at the time."[20]

"Proposed ages have been anywhere from 500 million years ago to older than 2.5 billion years."[21]

"The interplay of the two layers drives the geodynamo, the circulation of iron-rich fluid that powers the magnetic field. That field, surrounding the planet, protects Earth from being battered by the solar wind, a constant flow of charged particles ejected by the sun. As the inner core cools and crystallizes, the composition of the remaining fluid changes; more buoyant liquid rises like a plume while the cooling crystals sink. That self-sustaining, density-driven circulation generates a strong magnetic field with two opposing poles, north and south, or polarity."[19]

"Traces of magnetism in ancient rocks suggest that Earth had a magnetic field as far back as 4.2 billion years ago. That earlier field was likely generated by heat within the planet driving circulation within the molten core. But over time, computer simulations suggest, the heat-driven circulation wouldn’t have been strong enough alone to continue to power a strong magnetic field. Instead, the field began to shut down, signaled in the rock record by weakening intensities and rapid polarity reversals over millions of years. And then, at some point, Earth’s inner core began to crystallize, jump-starting the geodynamo and generating a new, strong magnetic field."[19]

Magnetic "inclusions within a suite of rocks in Quebec, Canada, dating to about 565 million years ago [...] — needlelike iron-rich grains that align themselves with the orientation of the magnetic field that existed when the rocks formed — show that the planet’s magnetic field was extremely weak at that time. These paleo-intensity values were 10 times less than the present magnetic field, lower than anything observed previously. It suggested there’s something fundamental going on in the core."[21]

"Combined with previous studies that have found that the magnetic field was also rapidly reversing polarity during that time period, the new result indicates that Earth’s field may have been on the point of collapse about 565 million years ago. That suggests that the inner core hadn’t yet solidified."[19]

"Because the rocks bearing the magnetic grains didn’t cool instantaneously but over a long time, the data represent an average field intensity for about a 100,000-year period. [A] true, persistent signal [was found]. Computer simulations have suggested that the weak field phase may have lasted much longer, from about 900 million to 600 million years ago."[20]

If "the core is cooling quickly, that means it was very hot in the recent past, and that the lower mantle was very hot in the recent past — so hot that both were molten just 1 billion to 2 billion years ago. We absolutely do not see that in the rock record."[22]

Palaeointensity "data from the Ediacaran (~565 million years old) Sept-Îles intrusive suite measured on single plagioclase and clinopyroxene crystals that hosted single-domain magnetic inclusions [indicates] a time-averaged dipole moment of ~0.7 × 1022 A m2, the lowest value yet reported for the geodynamo from extant rocks and more than ten times smaller than the strength of the present-day field."[23]

"Palaeomagnetic directional studies of these crystals define two polarities with an unusually high angular dispersion (S = ~26°) at a low latitude. Together with 14 other directional data sets that suggest a hyper-reversal frequency, these extraordinary low field strengths suggest an anomalous field behaviour, consistent with predictions of geodynamo simulations, high thermal conductivities and an Ediacaran onset age of inner core growth."[23]

Potassium cores[edit | edit source]

"Radioactive potassium [...] appears also to be a substantial source of heat in the Earth's core"[24]

"Radioactive potassium, uranium and thorium are thought to be the three main sources of heat in the Earth's interior, aside from that generated by the formation of the planet. Together, the heat keeps the mantle actively churning and the core generating a protective magnetic field."[24]

Much "less potassium [occurs] in the Earth's crust and mantle than [is] expected based on the composition of rocky meteors that supposedly formed the Earth. If, as some have proposed, the missing potassium resides in the Earth's iron core, how did an element as light as potassium get there, especially since iron and potassium don't mix?"[24]

At "the high pressures and temperatures in the Earth's interior, potassium can form an alloy with iron never before observed. During the planet's formation, this potassium-iron alloy could have sunk to the core, depleting potassium in the overlying mantle and crust and providing a radioactive potassium heat source in addition to that supplied by uranium and thorium in the core."[24]

The "new alloy [is created] by squeezing iron and potassium between the tips of two diamonds [a diamond anvil] to temperatures and pressures characteristic of 600-700 kilometers below the surface - 2,500 degrees Celsius and nearly 4 million pounds per square inch, or a quarter of a million times atmospheric pressure."[24]

"Our new findings indicate that the core may contain as much as 1,200 parts per million potassium -just over one tenth of one percent."[25]

"This amount may seem small, and is comparable to the concentration of radioactive potassium naturally present in bananas. Combined over the entire mass of the Earth's core, however, it can be enough to provide one-fifth of the heat given off by the Earth."[25]

"With one experiment, Lee and Jeanloz demonstrated that potassium may be an important heat source for the geodynamo, provided a way out of some troublesome aspects of the core's thermal evolution, and further demonstrated that modern computational mineral physics not only complements experimental work, but that it can provide guidance to fruitful experimental explorations,"[26]

"More experiments need to be done to show that iron can actually pull potassium away from the silicate rocks that dominate in the Earth's mantle."[27]

"They proved it would be possible to dissolve potassium into liquid iron."[27]

"Modelers need heat, so this is one source, because the radiogenic isotope of potassium can produce heat and that can help power convection in the core and drive the magnetic field. They proved it could go in. What's important is how much is pulled out of the silicate. There's still work to be done."[27]

"If a significant amount of potassium does reside in the Earth's core, this would clear up a lingering question - why the ratio of potassium to uranium in stony meteorites (chondrites), which presumably coalesced to form the Earth, is eight times greater than the observed ratio in the Earth's crust. Though some geologists have asserted that the missing potassium resides in the core, there was no mechanism by which it could have reached the core. Other elements like oxygen and carbon form compounds or alloys with iron and presumably were dragged down by iron as it sank to the core. But at normal temperature and pressure, potassium does not associate with iron."[24]

"Early in Earth's history, the interior temperature and pressure would not have been high enough to make this alloy."[25]

"But as more and more meteorites piled on, the pressure and temperature would have increased to the point where this alloy could form."[25]

"The Earth is thought to have formed from the collision of many rocky asteroids, perhaps hundreds of kilometers in diameter, in the early solar system. As the proto-Earth gradually bulked up, continuing asteroid collisions and gravitational collapse kept the planet molten. Heavier elements - in particular iron - would have sunk to the core in 10 to 100 million years' time, carrying with it other elements that bind to iron."[24]

"Gradually, however, the Earth would have cooled off and become a dead rocky globe with a cold iron ball at the core if not for the continued release of heat by the decay of radioactive elements like potassium-40, uranium-238 and thorium-232, which have half-lives of 1.25 billion, 4 billion and 14 billion years, respectively. About one in every thousand potassium atoms is radioactive."[24]

"The heat generated in the core turns the iron into a convecting dynamo that maintains a magnetic field strong enough to shield the planet from the solar wind. This heat leaks out into the mantle, causing convection in the rock that moves crustal plates and fuels volcanoes."[24]

Pure "iron and pure potassium [combined] in a diamond anvil cell [that] squeezed the small sample to 26 gigapascals of pressure while heating the sample with a laser above 2,500 Kelvin (4,000 degrees Fahrenheit), which is above the melting points of both potassium and iron. [Repeat] six times in the high-intensity X-ray beams of two different accelerators - Lawrence Berkeley National Laboratory's Advanced Light Source and the Stanford Synchrotron Radiation Laboratory - to obtain X-ray diffraction images of the samples' internal structure. The images confirmed that potassium and iron had mixed evenly to form an alloy, much as iron and carbon mix to form steel alloy."[24]

"In the theoretical magma ocean of a proto-Earth, the pressure at a depth of 400-1,000 kilometers (270-670 miles) would be between 15 and 35 gigapascals and the temperature would be 2,200-3,000 Kelvin."[28]

"At these temperatures and pressures, the underlying physics changes and the electron density shifts, making potassium look more like iron."[28]

"At high pressure, the periodic table looks totally different."[28]

"The work by Lee and Jeanloz provides the first proof that potassium is indeed miscible in iron at high pressures and, perhaps as significantly, it further vindicates the computational physics that underlies the original prediction."[26]

"If it can be further demonstrated that potassium would enter iron in significant amounts in the presence of silicate minerals, conditions representative of likely core formation processes, then potassium could provide the extra heat needed to explain why the Earth's inner core hasn't frozen to as large a size as the thermal history of the core suggests it should."[26]

There are three requisites for a dynamo to occur and subsequently operate:

  • An electrically conductive fluid medium such as a plasma or liquid iron
  • local magnetohydrodynamic instabilities
  • An energy source to create the local magnetohydrodynamic instabilities and to drive mechanical turbulence, motion, or shear within the fluid.

In the case of the Earth, the magnetic field is induced and constantly maintained by the convection of liquid iron in the outer core. A requirement for the induction of field is a rotating fluid. Rotation in the outer core is supplied by the Coriolis effect caused by the rotation of the Earth. The Coriolis force tends to organize fluid motions and electric currents into columns aligned with the rotation axis. Induction or creation of magnetic field is described by the induction equation:

where u is a velocity, B is the magnetic field, t is time, and is the magnetic diffusivity with electrical conductivity and permeability. The ratio of the second term on the right hand side to the first term gives the Magnetic Reynolds number, a dimensionless ratio of advection of a magnetic field to diffusion.

Tidal forces between celestial orbiting bodies causes friction that heats up the interiors of these orbiting bodies. This is known as tidal heating, and it helps create the liquid interior criteria, providing that this interior is conductive, that is required to produce a dynamo.

Siderophiles[edit | edit source]

Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number. The rarest elements in the crust (shown in yellow) are not the heaviest, but are rather the siderophile (iron-loving) elements in the Goldschmidt classification of elements. These have been depleted by being relocated deeper into the Earth's core. Their abundance in meteoroid materials is relatively higher. Additionally, tellurium and selenium have been depleted from the crust due to formation of volatile hydrides. Credit: Gordon B. Haxel, Sara Boore, and Susan Mayfield from USGS.{{free media}}

Def. "an element that forms alloys easily with iron and [may be] concentrated in the Earth's core"[29] is called a siderophile.

Siderophile (metal-loving) chemical elements include W, P, Co, Ni, Mo, Re, and Ir.[30]

"The platinum group elements (PGE: Os, Ir, Ru, Rh, Pt, and Pd) and Re are highly siderophile elements (HSE)".[31]

"We believe that silicon is a major element - about 5% [of the Earth's inner core] by weight could be silicon dissolved into the iron-nickel alloys."[32]

"The innermost part of Earth is thought to be a solid ball with a radius of about 1,200 km (745 miles)."[33]

"It is mainly composed of iron, which makes up an estimated 85% of its weight, and nickel, which accounts for about 10% of the core."[33]

"These difficult experiments are really exciting because they can provide a window into what Earth's interior was like soon after it first formed, 4.5 billion years ago, when the core first started to separate from the rocky parts of Earth."[34]

"But other workers have recently suggested that oxygen might also be important in the core."[34]

"In a way, these two options [oxygen was sucked into the core that would leave the rocky mantle surrounding the core depleted of the element or a larger amount of silicon had been incorporated in Earth's core more than four billion years ago, that would have left the rest of the planet relatively oxygen rich] are real alternatives that depend a lot on the conditions prevailing when Earth's core first began to form."[34]

Chromium minerals[edit | edit source]

This is a native chromium nugget. Credit: Neal Ekengren.{{fairuse}}
Fe-Cr phase diagram shows which phases are to be expected at equilibrium for different combinations of chromium content and temperature. Credit: Computational Thermodynamics Inc.{{fairuse}}

Native chromium such as the nugget in the image on the right is very rare. It is also a hard mineral, probably because of an oxide coating giving it a slight bluish cast.

"An unusual mineral association (diamond, SiC, graphite, native chromium, Ni-Fe alloy, Cr2+-bearing chromite), indicating a high-pressure, reducing environment, occurs in both the peridotites and chromitites."[35]

As the phase diagram for the Fe-Cr system on the left shows, chromium is bcc from 600°C on up to melting. Chromium is also bcc at room temperature and pressure.

Palladiums[edit | edit source]

This is a palladium nugget. Credit: Hudson Institute of Mineralogy. {{fairuse}}
This piece of native palladium is from the Mednorudyanskoye Cu Deposit, Nizhnii Tagil, Sverdlovskaya Oblast', Middle Urals, Urals Region, Russia. Credit: Hudson Institute of Mineralogy.{{fairuse}}

"Natural Palladium [like the nugget shown on the right] always contains some Platinum."[36]

This palladium nugget is from Bom Sucesso Creek, Serro, Minas Gerais, Brazil.

"(Pd,Cu) alloys, some with the approximate composition PdCu4, are reported by Kapsiotis et al. (2010)."[36]

The piece of native palladium [image on the left] from the Mednorudyanskoye Cu Deposit, Nizhnii Tagil, Sverdlovskaya Oblast', Middle Urals, Urals Region, Russia, probably contains some copper.

Iron meteorites[edit | edit source]

This iron meteorite left no impact crater in the desert. Credit: Geuology.com.{{fairuse}}

Iron meteorites, aka siderites, or ferrous meteorites are meteorites that consist overwhelmingly of iron–nickel alloys that usually consists of two mineral phases: kamacite and taenite. Most iron meteorites originate from planetary cores of planetesimals.[37]

Meteoric iron, a characteristic iron–nickel alloy, was used by various ancient peoples thousands of years before the Iron Age. Such iron, being in its native metallic state, required no smelting of ores.[38][39]

While they are fairly rare compared to the stony meteorites, comprising about 5.7% of witnessed falls, they have historically been heavily over-represented in meteorite collections.[40]

Iron meteorites account for almost 90% of the mass of all known meteorites, about 500 tons.[41]

On the right is apparently another iron meteorite discovered in a desert that left no crater.

All or nearly all, iron meteorites are magnetic. Passage through the Earth's magnetic field and the natural electric field of the Earth may cause these iron meteorites to slow down sufficiently so as to land without a crater.

Structural meteorites[edit | edit source]

Scanning electron micrograph shows the Widmanstätten microstructure of Zircaloy-4. Credit: Matheustunes.{{free media}}
This is a binary phase diagram of the iron-zirconum system. Credit: D. Arias and J.P. Abriata.{{fairuse}}

At temperatures below 1100 K, man-made zirconium alloys belong to the hexagonal crystal family (HCP), with its microstructure, revealed by chemical attack, showing needle-like grains typical of a Widmanstätten pattern as in the image on the right, which upon annealing below the phase transition temperature (α-Zr to β-Zr) become equiaxed with sizes varying from 3 to 5 μm.[42][43]

The structural classification of meteorites is based on the presence or absence of the Widmanstätten pattern, which can be assessed from the appearance of polished cross-sections that have been etched with acid. This is connected with the relative abundance of nickel to iron.

  • Ataxites (D): very high nickel, no Widmanstätten pattern, rare.
  • Hexahedrites (H): low nickel, no Widmanstätten pattern, may present Neumann lines.
  • Octahedrites (O): average to high nickel, Widmanstätten patterns, most common class, divided up on the basis of the width of the kamacite lamellae from coarsest to finest.[44]
  • Fine (Of): lamellae width 0.2–0.5 mm.
  • Finest (Off): lamellae width < 0.2 mm.
  • Coarse (Og): lamellae width 1.3–3.3 mm.
  • Coarsest (Ogg): lamellae width > 3.3 mm.
  • Medium (Om): lamellae width 0.5–1.3 mm.
  • Plessitic (Opl): a transitional structure between octahedrites and ataxites[45]

Ataxites (D)[edit | edit source]

Ataxites (D): very high nickel, no Widmanstätten pattern, rare.

Santiago Papasquiero meteorites[edit | edit source]

Ataxite (field of view ~2.5 cm across) - is a cut, polished, nitric acid-etched surface of the Santiago Papasquiero Meteorite, found in 1958 in Durango, Mexico. Credit: James St. John.{{free media}}

The Santiago Papasquiero meteorites consist of a finely crystalline mix of kamacite & taenite, plus other minor minerals. Santiago Papasquiero is a strange ataxite that appears to be a completely metamorphosed and recrystallized octahedrite. Most recrystallized octahedrites still retain vague hints of the original Widmanstätten structure. This meteorite doesn't have any, so it isn’t an octahedrite - it’s an ataxite.

Published chemical info. indicates that Santiago Papasquiero has 7.5% nickel content overall. The kamacite component has 6.8% Ni. The taenite component has 30% Ni.

Hexahedrites (H)[edit | edit source]

Hexahedrites (H): low nickel, no Widmanstätten pattern, may present Neumann lines.

Hexahedrites are a structural class of iron meteorite, composed almost exclusively of the nickel–iron alloy kamacite and are lower in nickel content than the octahedrites.[46] The nickel concentration in hexahedrites is always below 5.8% and only rarely below 5.3%.[47]

Neumann lines: parallel lines that cross each other at various angles, and are indicative of impact shock on the parent body.[48]

Concentrations of trace elements (germanium, gallium and iridium) are used to separate the iron meteorites into chemical classes, which correspond to separate asteroid parent bodies, where chemical classes that include hexahedrites are:[49]

Coahuila meteorites[edit | edit source]

Coahuila fragment is in the Harvard Museum of Natural History. Credit: DerHexer.{{free media}}

Only fragments found in Coahuila, that are hexahedrites and fall into the IIAB meteorite group should be called Coahuila meteorites.[50][51]

The mineral Daubréelite was first described in this meteorite.

  1. Group: IIAB meteorites.[50]
  2. Structural classification: Hexahedrite.
  3. Country: Mexico.
  4. Region: Coahuila.
  5. Coordinates: 28°42'N 102°44'W.
  6. Observed fall: No.
  7. Found date: 1837.[50]
  8. TKW: 2,100 kilograms (4,600 lb).

Octahedrites[edit | edit source]

Phase diagram for meteoric iron shows the phase boundaries as a function of temperature and amount of nickel in the system, the field for Octahedrites is highlighted. Credit: Tobias1984.{{free media}}
Octahedron is shown slowly turning. Credit: Peter Steinberg.{{free media}}
Different cuts of the octahedron produce different Widmanstätten patterns. Credit: Davide Bolsi.{{free media}}

Octahedrites derive their name from the crystal structure paralleling an octahedron.

In gaps between the kamacite and taenite lamellae, a fine-grained mixture called plessite is often found, with an iron nickel phosphide, schreibersite, in most nickel-iron meteorites, an iron-nickel-cobalt carbide, cohenite, graphite and troilite in rounded nodules up to several cm in size.[52]

Cutting the meteorite along different planes affects the shape and direction of Widmanstätten figures because kamacite lamellae in octahedrites are precisely arranged. Opposite faces are parallel so, although an octahedron has 8 faces, there are only 4 sets of kamacite plates. Iron and nickel-iron form crystals with an external octahedral structure only very rarely, but these orientations are still plainly detectable crystallographically without the external habit. Cutting an octahedrite meteorite along different planes (or any other material with octahedral symmetry, which is a sub-class of cubic symmetry) will result in one of these cases:

  • perpendicular cut to one of the three (cubic) axes: two sets of bands at right angles each other
  • parallel cut to one of the octahedron faces (cutting all 3 cubic axes at the same distance from the crystallographic center) : three sets of bands running at 60° angles each other
  • any other angle: four sets of bands with different angles of intersection.

Octahedrites can be grouped by the dimensions of kamacite lamellae in the Widmanstätten pattern, which are related to the nickel content:[53]

  • Coarsest octahedrites, lamellae width >3.3 mm, 5-9% Ni, symbol Ogg
  • Coarse octahedrites, lamellae 1.3-3.3 mm, 6.5-8.5% Ni, symbol Og
  • Medium octahedrites, lamellae 0.5-1.3 mm, 7-13% Ni, symbol Om
  • Fine octahedrites, lamellae 0.2-0.5 mm, 7.5-13% Ni, symbol Of
  • Finest octahedrites, lamellae <0.2 mm, 17-18% Ni, symbol Off
  • Plessitic octahedrites, kamacite spindles, a transitional structure between octahedrites and ataxites,[54] 9-18% Ni, symbol Opl

Zacatecas meteorites[edit | edit source]

The Zacatecas Meteorite was found in 1782 in Zacatecas Mexico, weighing 780kg. Credit: Thelmadatter.{{free media}}

Brecciated octahedrite.

Fine octahedrites (Of)[edit | edit source]

Fine octahedrites, 7.4–9.4% Ni, 1.6–2.4 ppm Ga, 0.09–0.14 ppm Ge, 0.4-4 ppm Ir, Ge-Ni correlation positive.

Muonionalusta meteorites[edit | edit source]

The Muonionalusta meteorite, on loan to the Prague National Museum in 2010, is the largest meteorite ever exhibited in the Czech Republic. Credit: Krenakarore.{{free media}}
Slice (across 9.6 cm) of a Muonionalusta meteorite fragment, shows the Widmanstätten pattern. Credit: R. Tanaka.{{free media}}

The first fragment of the Muonionalusta meteorite was found in 1906 near the village of Kitkiöjärvi.[55][56] Around forty pieces are known today, some being quite large, other fragments have been found in a 25 by 15 kilometres (15.5 mi × 9.3 mi) area in the Pajala district of Norrbotten County, approximately 140 kilometres (87 mi) north of the Arctic Circle.

The meteorite was first described in 1910 by Professor A. G. Högbom, who named it after the nearby place Muonionalusta on the Muonio River.[57] The Muonionalusta meteorite, probably the oldest known meteorite (4.5653 ± 0.0001 billion years),[58] marks the first occurrence of stishovite in an iron meteorite.

It is the oldest discovered meteorite impacting the Earth during the Quaternary Period, about one million years ago and is quite clearly part of the iron core or mantle of a planetoid, which shattered into many pieces upon its fall on our planet.[59] Since landing on Earth the meteorite has experienced four ice ages, was unearthed from a glacial moraine in the northern tundra], and has a strongly weathered surface covered with cemented faceted pebbles.

New analysis of this strongly shock-metamorphosed iron meteorite has shown a content of 8.4% nickel and trace amounts of rare elements—0.33 ppm gallium, 0.133 ppm germanium and 1.6 ppm iridium and contains the minerals chromite, daubréelite, schreibersite, akaganéite and inclusions of troilite.[57]

For the first time, analysis has proved the presence of a form of quartz altered by extremely high pressure—stishovite,[57] probably a pseudomorphosis after tridymite. From the article "First discovery of stishovite in an iron meteorite": Stishovite, a high pressure polymorph of SiO2, is an exceptionally rare mineral...and has only been found in association with a few meteorite impact structures.... Clearly, the meteoritic stishovite cannot have formed by isostatic pressure prevailing in the core of the parent asteroid.... One can safely assume then that stishovite formation (in the Muonionalusta meteorite) is connected with an impact event. The glass component might have formed directly as a shock melt....[55]

The lead isotope dating in the Muonionalusta meteorite concluded the stishovite was from an impact event hundreds of millions of years ago: "The presence of stishovite signifies that this meteorite was heavily shocked, possibly during the 0.4 Ga [billion years] old breakup event indicated by cosmic ray exposure...."[58]

Fragments of the Muonionalusta meteorite are held by numerous institutions around the world.

  • Geological Institute, Uppsala, 15 kilograms (33 lb).
  • Naturhistorisches Museum , Vienna, 96 g.
  • Museum für Naturkunde, Berlin, 82 g.
  • Max Planck Society (Max Planck Institute), Mainz, 96.3 g.
  • Paneth Collection (also at the Max Planck Institute), Mainz, 142.5 g.
  • National Museum of Natural History, Washington, 197 g.
  • American Museum of Natural History, New York, 84 g.
  • Field Museum of Natural History, Chicago, 65.2 g.
  • University of California, Los Angeles, 55 g.[60]
  • Vernadsky State Geological Museum, Moscow 2404 g.
  • Observatory and Planetarium Brno, Czech Republic, 21 kg.
  • Rahmi M. Koç Museum, Istanbul.
  1. Type: IVA (Of).
  2. Class: Octahedrite.
  3. Group: Iron.
  4. Structural classification: Fine Octahedrite.
  5. Composition: Ni, Ga, Ge.
  6. Country: Sweden.
  7. Region: Norrbotten.
  8. Coordinates: 67°48'N 23°6.8'E.
  9. Observed fall: No.
  10. Found date: 1906.
  11. Strewn field: Yes.

Finest octahedrites (Off)[edit | edit source]

  • Finest octahedrites, lamellae <0.2 mm, 17-18% Ni, symbol Off.

Coarse octahedrites (Og)[edit | edit source]

  • Coarse octahedrites, lamellae 1.3-3.3 mm, 6.5-8.5% Ni, symbol Og.

Coarsest octahedrites Ogg[edit | edit source]

  • Coarsest octahedrites, lamellae width >3.3 mm, 5-9% Ni, symbol Ogg.

Morasko meteorites[edit | edit source]

261.8 kg heavy fragment is from the Morasko meteorite. Credit: Chmee2.{{free media}}

"The Morasko meteorite belongs to the coarse octahedrite group and contains 92% Fe, 6.7% Ni, and less than 1% Co, P, S, Cu, and C."[61]

"The Morasko meteorite belongs to the coarse octahedrite (Ogg) group (J. Polkrzywnicki, 1964; B, Dominik, 1976)."[61]

"The Morasko meteorite contains the following minerals: kamacite, the 𝛂-phase of iron-nickel about 90 %, tenite, the 𝛄-phase of iron-nickel 0.5 %, troilite several per cent, graphite about 1 %, cloftonite, schreibersite about 1.5 %, rhabdite about 1 %, cohenite, sphalerite about 0.2 %, whitlockite, as well as secondary minerals magnetite and goethite (B. Dominik, 1976)."[61]

Medium octahedrites (Om)[edit | edit source]

  • Medium octahedrites, lamellae 0.5-1.3 mm, 7-13% Ni, symbol Om.

Plessitic octahedrites (Opl)[edit | edit source]

  • Plessitic octahedrites, kamacite spindles, a transitional structure between octahedrites and ataxites,[62] 9-18% Ni, symbol Opl.

Asteroid parental bodies[edit | edit source]

A newer chemical classification scheme based on the proportions of the trace elements Ga, Ge and Ir separates the iron meteorites into classes corresponding to distinct asteroid parent bodies.[63] This classification is based on diagrams that plot nickel content against different trace elements (e.g. Ga, Ge and Ir). The different iron meteorite groups appear as data point clusters.[37][64]

There were originally four of these groups designated by the Roman numerals I, II, III, IV. When more chemical data became available these were split, e.g. Group IV was split into IVA meteorites (IVA) and IVB meteorites. Even later some groups got joined again when intermediate meteorites were discovered, e.g. IIIA and IIIB were combined into the IIIAB meteorites.[65]

In 2006 iron meteorites were classified into 13 groups (one for uncategorized irons):[37]

  • IAB meteorite (IAB).
  • IA: Medium and coarse octahedrites, 6.4-8.7% Ni, 55-100 ppm Ga, 190-520 ppm Ge, 0.6–5.5 ppm Ir, Ge-Ni correlation negative.
  • IB: Ataxites and medium octahedrites, 8.7–25% Ni, 11–55 ppm Ga, 25–190 ppm Ge, 0.3-2 ppm Ir, Ge-Ni correlation negative.
  • IC meteorites (IC): 6.1–6.8% Ni. The Ni concentrations are positively correlated with As (4–9 μg/g), Au (0.6–1.0 μg/g) and P (0.17–0.40%) and negatively correlated with Ga (54–42 μg/g), Ir (9–0.07 μg/g) and W (2.4–0.8 μg/g).
  • IIAB meteorites (IIAB).
  • IIA: Hexahedrites, 5.3–5.7% Ni, 57–62 ppm Ga, 170–185 ppm Ge, 2-60ppm Ir.
  • IIB: Coarsest octahedrites, 5.7–6.4% Ni, 446-59 pm Ga, 107–183 ppm Ge, 0.01–0.5 ppm Ir, Ge-Ni correlation negative.
  • IIC meteorite (IIC0: Plessitic octahedrites, 9.3–11.5% Ni, 37–39 ppm Ga, 88–114 ppm Ge, 4–11 ppm Ir, Ge-Ni correlation positive.
  • IID meteorite (IID): Fine to medium octahedrites, 9.8–11.3%Ni, 70–83 ppm Ga, 82–98 ppm Ge, 3.5–18 ppm Ir, Ge-Ni correlation positive.
  • IIE iron meteorite (IIE): octahedrites of various coarseness, 7.5–9.7% Ni, 21–28 ppm Ga, 60–75 ppm Ge, 1–8 ppm Ir, Ge-Ni correlation absent.
  • IIF.
  • IIG meteorites (IIG): Hexahedrites with coarse schreibersite. Meteoric iron has low nickel concentration.[66]
  • IIIAB meteorites (IIIAB): Medium octahedrites, 7.1–10.5% Ni, 16–23 ppm Ga, 27–47 ppm Ge, 0.01-19 ppm Ir.
  • IIICD meteorite (IIICD): Ataxites to fine octahedrites, 10–23% Ni, 1.5–27 ppm Ga, 1.4–70 ppm Ge, 0.02–0.55 ppm Ir.
  • IIIE meteorites (IIIE): Coarse octahedrites, 8.2–9.0% Ni, 17–19 ppm Ga, 3–37 ppm Ge, 0.05-6 ppm Ir, Ge-Ni correlation absent.
  • IIIF meteorites (IIIF): Medium to coarse octahedrites, 6.8–7.8% Ni,6.3–7.2 ppm Ga, 0.7–1.1 ppm Ge, 1.3–7.9 ppm Ir, Ge-Ni correlation absent.
  • IVA meteorites (IVA): Fine octahedrites, 7.4–9.4% Ni, 1.6–2.4 ppm Ga, 0.09–0.14 ppm Ge, 0.4-4 ppm Ir, Ge-Ni correlation positive.
  • IVB meteorite (IVB): Ataxites, 16–26% Ni, 0.17–0.27 ppm Ga, 0,03–0,07 ppm Ge, 13–38 ppm Ir, Ge-Ni correlation positive.
  • Ungrouped meteorites. This is actually quite a large collection (about 15% of the total) of over 100 meteorites that do not fit into any of the larger classes above, and come from about 50 distinct parent bodies.

The iron meteorites were previously divided into two classes: magmatic irons and non magmatic or primitive irons. Now this definition is deprecated.

Iron class Groups
Nonmagmatic meteorite (Nonmagmatic or primitive iron meteorites) IAB meteorites (IAB), IIE iron meteorite (IIE)
Magmatic iron meteorites IC, IIAB, IIC, IID, IIF, IIG meteorites (IIG), IIIAB, IIIE, IIIF, IVA, IVB meteorites (IVB)

IAB meteorites[edit | edit source]

Canyon Diablo meteorites[edit | edit source]

Octahedrite - large cut-polished-nitric acid etched slice of the Canyon Diablo Meteorite that fantastically displays the Widmanstätten structure. Credit: James St. John.{{free media}}

Meteor Crater (Barringer Crater) in the Arizona desert was formed by the impact of an octahedrite ~49,000 years ago during the Late Pleistocene. The rock shown here is a fragment of the impactor, the Canyon Diablo Meteorite. Such fragments have been collected for decades from the desert surrounding the crater. Canyon Diablo is composed of ~90% kamacite, ~1-4% taenite, and up to 8.5% troilite-graphite nodules (FeS & C). The original mass has been estimated to be 100 feet across & about 60,000 tons. Canyon Diablo rocks are well dated to 4.55 billion years.

  1. Group: IAB-MG.

Mundrabilla meteorites[edit | edit source]

Main mass of Mundrabilla meteorite weighs 12.4 tonnes, Western Australia Museum. Credit: Graeme Churchard.{{free media}}
This is the second largest piece of the Mundrabilla meteorite. Credit: R. B. Wilson and A. M. Cooney.{{fairuse}}
This is one of the larger fragments of the Mundrabilla meteorite. Credit: R. B. Wilson and A. M. Cooney.{{fairuse}}
Still covered in some of the sediment and partial weathering produced after its fall is this small fragment. Credit: R. B. Wilson and A. M. Cooney.{{fairuse}}
One small fragment looks like it is thumb-printed. Credit: R. B. Wilson and A. M. Cooney.{{fairuse}}
About 9 cm on edge, this piece of the Mundrabilla meteorite has a hole in it. Credit: R. B. Wilson and A. M. Cooney.{{fairuse}}

"The Mundrabilla iron meteorite and meteorite irons found around the Nullarbor Plain in Western Australia may have all been found above or just below the surface."[67]

The main mass of the Mundrabilla meteorite weighs 12.4 tonnes and is shown first on the right.

"There are a number of large Mundrabilla iron meteorites but there are also the much smaller and strangely shaped Mundrabilla meteorite irons."[67]

"In April 1966, two large masses estimated to be 10-12 tons and 4-6 tons [second on the left], later named Mundrabilla, were found approximately 200 yards (ca. 183 m) apart and described by the finders R. B. Wilson and A. M. Cooney."[67]

"The 12.4 tonne main mass (recently accurately weighed) of the Mundrabilla meteorite shower is the largest meteorite yet found in Australia. In all, some 22 tonnes of fragments of this ancient meteorite shower have been recovered."[67]

"Mundrabilla meteorite irons are strange little pieces of iron, twisted into odd shapes."[67]

Second on the right is perhaps the third largest piece of the Mundrabilla meteorite.

The second image on the left is another piece of the Mundrabilla meteorite still covered in some of the sediment and partial weathering produced after its fall.

One small fragment of the Mundrabilla iron meteorite looks like it is thumb-printed. It is the third image down on the right.

The last fragment here of the Mundrabilla iron meteorite on the left third down is about 9 cm on edge and has a hole in it.

  1. Group: IAB.

Toluca meteorites[edit | edit source]

A 500 g endcut is from the Toluca iron meteorite (coarse octahedrite, class IA), polished and etched face, displaying Widmanstätten Pattern. Credit: H. Raab.{{free media}}

The meteorites probably crashed towards the Earth more than 10,000 years earlier.[68]

These iron meteorites are a coarse octahedrite, chemical type IAB meteorites-sLL.[69]

The mean composition is 90.5% Fe and 8.1% Ni.[46]

They often contain large troilite inclusions.

  1. Group: IAB meteorites-sLL.
  2. Structural classification: Coarse Octahedrite.
  3. Composition: 90.5% Fe; 8.1% Ni.
  4. Country: Mexico.
  5. Region: Toluca Valley, Jiquipilco, Mexico State.
  6. Coordinates: 19°27′N 99°35′W / 19.45°N 99.583°W / 19.45; -99.583.[46]
  7. Fall date: >10,000 years ago.
  8. Found date: about 1776.
  9. TKW: 3 tonnes.

IA meteorites[edit | edit source]

  • IA: Medium and coarse octahedrites, 6.4-8.7% Ni, 55-100 ppm Ga, 190-520 ppm Ge, 0.6–5.5 ppm Ir, Ge-Ni correlation negative.

IB meteorites[edit | edit source]

  • IB: Ataxites and medium octahedrites, 8.7–25% Ni, 11–55 ppm Ga, 25–190 ppm Ge, 0.3-2 ppm Ir, Ge-Ni correlation negative.

IC meteorites[edit | edit source]

  • IC meteorites (IC): 6.1–6.8% Ni. The Ni concentrations are positively correlated with As (4–9 μg/g), Au (0.6–1.0 μg/g) and P (0.17–0.40%) and negatively correlated with Ga (54–42 μg/g), Ir (9–0.07 μg/g) and W (2.4–0.8 μg/g).

IIAB meteorites[edit | edit source]

Sikhote-Alin meteorites[edit | edit source]

Disk has troilite inclusions, a recrystallized rim from high temperatures during flight through the atmosphere, and Neumann lines. Credit: André Knöfel.{{free media}}
A 1.7 kg individual meteorite from the Sikhote Alin meteorite shower (coasrsest octahedrite, class IIAB). Credit: H. Raab.{{free media}}

Large iron meteorite falls have been witnessed and fragments recovered but never before, in recorded history, a fall of this magnitude.[70] An estimated 23 tonnes[71] of fragments survived the fiery passage through the atmosphere and reached the Earth.

As the meteor, traveling at a speed of about 14 km/s (8.7 mi/s), entered the atmosphere, it began to break apart, and the fragments fell together, some burying themselves 6 metres (20 ft) deep.[72] At an altitude of about 5.6 km (3.5 mi), the largest mass apparently broke up in a violent explosion called an air burst.

This orbit was ellipse-shaped, with its point of greatest distance from the sun situated within the asteroid belt, similar to many other small bodies crossing the orbit of the Earth.[73] Such an orbit was probably created by collisions within the asteroid belt.

Sikhote-Alin is a massive fall with the pre-atmospheric mass of the meteoroid estimated at approximately 90,000 kilograms (200,000 lb).[74] A more recent estimate by Tsvetkov (and others) puts the mass at around 100,000 kg (220,000 lb).[75]

Estimated the post-atmospheric mass of the meteoroid at some 23,000 kilograms (51,000 lb).

The Sikhote-Alin meteorite is classified as an iron meteorite belonging to the meteorite group IIAB and with a coarse octahedrite structure. It is composed of approximately 93% iron, 5.9% nickel, 0.42% cobalt, 0.46% phosphorus, and 0.28% sulfur, with trace amounts of germanium and iridium. Minerals present include taenite, plessite, troilite, chromite, kamacite, and schreibersite.[46]

  1. Group: IIAB
  2. Structural classification: Octahedrite, coarsest
  3. Composition= 93% Fe, 5.9% Ni, 0.42% Co, 0.46% P, 0.28% S
  4. Country= Russia
  5. Region= Sikhote-Alin Mountains, Primorsky Krai]], Far Eastern Federal District
  6. Coordinates: 46°09′36″N 134°39′12″E / 46.16°N 134.65333°E / 46.16; 134.65333[71]
  7. Observed fall: Yes
  8. Fall date: February 12, 1947
  9. Weight: >23 tonnes (25 short tons)[71]
  10. Strewn field: Yes

"Group lIB. 5.90% Ni, 0.42% Co, 0.46% P, 0.28% S, 52 ppm Ga, 161 ppm Ge , 0.03 ppm Ir."[46]

IIA meteorites[edit | edit source]

  • IIA: Hexahedrites, 5.3–5.7% Ni, 57–62 ppm Ga, 170–185 ppm Ge, 2-60ppm Ir.

IIB meteorites[edit | edit source]

  • IIB: Coarsest octahedrites, 5.7–6.4% Ni, 446-59 pm Ga, 107–183 ppm Ge, 0.01–0.5 ppm Ir, Ge-Ni correlation negative.

Ainsworth meteorites[edit | edit source]

Ainsworth Meteorite is a group IIB iron meteorite that was found in 1907 in Brown County, northern Nebraska, USA. Credit: James St. John.{{free media}}

Ainsworth meteorite is texturally classified as a coarsest octahedrite (aka granular hexahedrite; aka kamacite octahedrite), meaning it has the largest size of metal crystals known in iron meteorites, and lacks thin, criss-crossing blades, (Me 1059, FMNH public display, Field Museum of Natural History, Chicago, Illinois, USA).

IIC meteorites[edit | edit source]

  • IIC meteorite (IIC0: Plessitic octahedrites, 9.3–11.5% Ni, 37–39 ppm Ga, 88–114 ppm Ge, 4–11 ppm Ir, Ge-Ni correlation positive.

IID meteorites[edit | edit source]

  • IID meteorite (IID): Fine to medium octahedrites, 9.8–11.3%Ni, 70–83 ppm Ga, 82–98 ppm Ge, 3.5–18 ppm Ir, Ge-Ni correlation positive.

IIE meteorites[edit | edit source]

  • IIE iron meteorite (IIE): octahedrites of various coarseness, 7.5–9.7% Ni, 21–28 ppm Ga, 60–75 ppm Ge, 1–8 ppm Ir, Ge-Ni correlation absent.

IIF meteorites[edit | edit source]

IIG meteorites[edit | edit source]

Phase diagram shows the suspected cooling path of the parent body. Credit: .{{free media}}

While cooling the parent body reached the IIAB field, then followed the field to the eutectic point where the remaining melt cavities formed the IIG meteorites.[76]

Trace elements of IIAB meteorites and IIG meteorites are offset, which was interpreted as (1) the two groups forming on a separate planetesimal or (2) melt immiscibility, while the planetesimal was cooling off: first meteoric iron crystallized into a network of cavities and channels, but eventually crystallization cut off the channels and made cavities of trapped melt, when the remaining melt reached the eutectic point, the cavities crystallized a mixture of schreibersite and meteoric iron.[76]

The matrix of this process would form the IIAB meteorites, while the cavities would form the IIG meteorites.[76]

  • IIG meteorites (IIG): Hexahedrites with coarse schreibersite. Meteoric iron has low nickel concentration.[76]

The Bellsbank meteorite, La Primitiva meteorite and Tombigbee meteorite meteorites were iron meteorites that were found to have chemical and structural similarities.[77]

It was proposed that the three meteorites should be grouped into the "Bellsbank Trio" grouplet.[78][79]

The grouplet status that requires five specimen was filled by the Twannberg meteorite and by the Guanaco meteorite.[80]

The sixth member is the Auburn meteorite.[81]

IIGs contain large amounts of phosphorus in the form of schreibersite and very low concentrations of sulfur.[76][80]

  1. Class: Magmatic.[76]
  2. Structural classification: Hexahedrite.[76]
  3. Parent body: IIG-IIAB.[76]
  4. Composition: Meteoric iron (kamacite), nickel (4.1 to 4.9 %), much schreibersite (phosphorus), little sulfur.[76]
  5. Number of specimens: 6.[76]

Bellsbank meteorites[edit | edit source]

Only one specimen with a mass of 38 kilograms (84 lb) was dug out from a field near Bellsbank, northwest of Kimberley, South Africa.[82]

The meteorite was first described in 1959.[83]

Upon etching the meteorite shows Neumann lines.[83] The meteoric iron has nickel concentrations as low as 1.6%.[76]

After 5 meteorites were found the grouplet called "Bellsbank Trio" was renamed IIG meteorites (IIG group).[76]

  1. Type: Iron meteorite.
  2. Group: IIG.[76]
  3. Structural classification: Hexahedrite.[82]
  4. Parent body: IIG-IIAB.[76]
  5. Composition: Meteoric iron (Kamacite), Schreibersite
  6. Country: Bellsbank, South Africa.
  7. Coordinates: 28°5'S 24°5'E.[82]
  8. Observed fall: No
  9. Found date: 1955[82]
  10. TKW: 38 kilograms (84 lb)[82]

Twannberg meteorites[edit | edit source]

The Twannberg meteorite is the only meteorite of the IIG group found in Europe and the largest meteorite ever found in Switzerland.[84]

The first fragment (15.91 kilograms (35.1 lb)) was found on 9 May 1984 in a barley field near Twann, after it had been ploughed (Twannberg I), and two additional fragments were found in an unnatural setting: one fragment (II) win an attic in Twann and another (III) in the Natural History Museum of Bern (Naturhistorisches Museum Bern), in a collection received from the Museum Schwab in Biel where it had been labeled as hematite.[84] Twannberg IV, V and VI were found in the creek Twannbach.[80]

The meteorite is named after Twannberg (from German: Twann mountain), a mountain that lies north of Twann.

The find location is a glacial till deposit, paired with minerals found in the oxidized surface of the meteorite are an indicator that the meteorite fell on the Rhone glacier and was transported to Twann during the Würm ice age and then deposited there.[80]

The preatmospheric mass was estimated to be at least 11,000 kilograms (24,000 lb), where the surface of the meteorite is covered in an oxidation layer.[80]

  1. Type: Iron meteorite.
  2. Group: IIG meteorites.[76]
  3. Structural classification: Hexahedrite.
  4. Parent body: IIG-IIAB.
  5. Composition: Meteoric iron 5.1 % Ni (Kamacite), Schreibersite.[84]
  6. Country: Switzerland.
  7. Region: Canton of Bern.
  8. Coordinates: 47°7'28"N 7°10'44"E.
  9. Observed fall: No.
  10. Found date: 9 May 1984.
  11. TKW: 20.69 kilograms (45.6 lb) (6 fragments).[80]

IIIAB meteorites[edit | edit source]

  • IIIAB meteorites (IIIAB): Medium octahedrites, 7.1–10.5% Ni, 16–23 ppm Ga, 27–47 ppm Ge, 0.01-19 ppm Ir.

Cape York meteorites[edit | edit source]

Ahnighito fragment of the Cape York meteorite weighs 34 tons and is in the AMNH. Credit: Mike Cassano.{{free media}}
Widmanstätten pattern is shown for the Cape York meteorite. Credit: Captmondo.{{free media}}
Slice of Agpalilik is in the Geological Museum in Copenhagen. Credit: Michael B. H..{{free media}}
Agpalilik is outside the Geological Museum in Copenhagen. Credit: Michael B. H..{{free media}}

"Cape York iron meteorites are separate lumps of iron but have been grouped together as fragments of the same iron meteorite, as they are found around the same location. The iron pieces known as the Women and the Dog were found about 25 meters from each other on the mainland and Ahnighito was found on an island. They were found above the ground and with no visible crater around them, even for the largest one called Ahnighito."[85]

Cape York is in Savissivik, Northwest Greenland. Ahnighito (the Tent) weighs 31 metric tons; the Woman, weighs 3 metric tons; the Dog, weighs 400 kilograms, Savik I 3.4 tons, Savik II 7.8 kg, and Agpalilik about 15 tons.[86]

"The meteorite lay on an ice-free slope 500 m from the shore and was partly covered with gneiss boulders. There was no crater and no crushing of rocks discovered."[86]

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. In addition to many small fragments, at least eight large fragments with a total mass of 58 tons have been recovered,[87] the largest weighing 31 tonnes (31 long tons; 34 short tons). The meteorite is loosely named after the location where the largest fragment was found: 23 miles (37 km) east of Cape York, in Savissivik, Meteorite Island, Greenland.

The largest fragment was recovered in an area where the landscape consists of "flowing" gravel or clay-like sediments on permafrost, indicating that it had been in place for no more than a few thousand years.[87] Other estimates have put the date of the fall as 10,000 years ago.[88]

  1. Group: IIIAB
  2. Structural classification: Octahedrite, medium
  3. Composition= 7.58% Ni, 19.2 ppm Ga, 36.0 ppm Ge, 5.0 ppm Ir
  4. Country: Greenland
  5. Region= Avannaata
  6. Coordinates: 76°08′N 64°56′W / 76.133°N 64.933°W / 76.133; -64.933[89]
  7. Fall date: A few thousand years ago[87]
  8. Found_date: Prehistoric[87]
  9. TKW: 58,200 kg[89]

Each of the most important fragments of Cape York has its own name (listed in order of discovery date by foreigners):

  1. Ahnighito (the Tent), 30,900 kilograms (68,100 lb),[90] 1884–1897, Meteorite Island, 76°04'N – 64°58'W
  2. Woman, 3,000 kilograms (6,600 lb),[90] 1897, Saveruluk, 76°09'N – 64°56'W
  3. Dog, 400 kilograms (880 lb), 1897, Saveruluk, 76°09'N – 64°56'W
  4. Savik I, 3,400 kilograms (7,500 lb),[90] 1913, Savequarfik, 76°08'N – 64°36'W
  5. Thule, 48.6 kilograms (107 lb), summer 1955, Thule, 76°32'N – 67°33'W[91]
  6. Savik II, 7.8 kilograms (17 lb), 1961, Savequarfik, 76°08'N – 64°36'W
  7. Agpalilik (the Man), 20,000 kilograms (44,000 lb), 1963, Agpalilik, 76°09'N – 65°10'W[90]
  8. Tunorput, 250 kilograms (550 lb), 1984

Laguna Manantiales meteorites[edit | edit source]

This image is a cross-section of the Laguna Manantiales meteorite showing Widmanstätten patterns. Credit: Aram Dulyan.{{free media}}
The Laguna Manantiales meteorite is on loan from the UCLA Institute of Geophysics & Planetary Physics. Credit: Kaldari.{{free media}}

The Laguna Manantiales meteorite is an iron octahedrite, class IIIAB, 92 kg, found at 48°35' S, 67°25' W, in 1945, at Laguna Manantiales, Santa Cruz, Argentina.[92]

Willamette Meteorites[edit | edit source]

Close-up is of the Willamette meteorite on display at the American Museum of Natural History in New York City. Credit: David R. Tribble.{{free media}}
The Willamette meteorite is on display at the American Museum of Natural History in New York City. Credit: David R. Tribble.{{free media}}
The American Museum of Natural History ensures access to the Willamette Meteorite. Credit: Ellen V. Futter.{{fairuse}}

The Willamette meteorite, officially named Willamette[93] and originally known as Tomanowos by the Clackamas Chinook[94][95]

It is the largest meteorite found in the United States and the sixth largest in the world.[96][97] There was no impact crater at the discovery site; researchers believe the meteorite landed in what is now Canada or Montana, and was transported as a glacial erratic to the Willamette Valley during the Missoula Floods at the end of the last Ice Age (~13,000 years ago).[98]

The Willamette Meteorite weighs about 34,200 pounds (15,500 kg). It is classified as a type III iron meteorite, being composed of over 91% iron and 7.62% nickel, with traces of cobalt and phosphorus. The approximate dimensions of the meteorite are 10 feet (3 m) tall by 6.5 feet (2 m) wide by 4.25 feet (1.3 m) deep. Most iron meteorites like Willamette have originated from the differentiated core of planetesimals or asteroids that collided with another object. Willamette has a recrystallized structure with only traces of a medium Widmanstätten pattern; it is the result of a significant impact-heating event on the parent body.[97][99] The Willamette Meteorite contains higher concentrations of various metals that are quite rare in Earth's crust. For example, iridium, one of the least abundant elements in Earth's crust, is found in the Willamette Meteorite at a concentration of 4.7 ppm vs. having an average mass fraction of 0.001 ppm in crustal rock, thousands of times more concentrated than in the crust.[100]

  1. Group: IIIAB meteorites.
  2. Structural classification: Medium Octahedrite.
  3. Composition: 91% Fe, 7.62% Ni, 18.6ppm Ga, 37.3ppm Ge, 4.7ppm Ir.
  4. Coordinates of find: 45°22′N 122°35′W / 45.367°N 122.583°W / 45.367; -122.583[101]
  5. Total known weight: 14,150 kilograms (15.60 short tons)[102]

IIICD meteorites[edit | edit source]

  • IIICD meteorite (IIICD): Ataxites to fine octahedrites, 10–23% Ni, 1.5–27 ppm Ga, 1.4–70 ppm Ge, 0.02–0.55 ppm Ir.

IIIE meteorites[edit | edit source]

  • IIIE meteorites (IIIE): Coarse octahedrites, 8.2–9.0% Ni, 17–19 ppm Ga, 3–37 ppm Ge, 0.05-6 ppm Ir, Ge-Ni correlation absent.

IIIF meteorites[edit | edit source]

  • IIIF meteorites (IIIF): Medium to coarse octahedrites, 6.8–7.8% Ni,6.3–7.2 ppm Ga, 0.7–1.1 ppm Ge, 1.3–7.9 ppm Ir, Ge-Ni correlation absent.

IVA meteorites[edit | edit source]

  • IVA meteorites (IVA): Fine octahedrites, 7.4–9.4% Ni, 1.6–2.4 ppm Ga, 0.09–0.14 ppm Ge, 0.4-4 ppm Ir, Ge-Ni correlation positive.

Gibeon meteorites[edit | edit source]

Widmanstätten texture is in the surface of an etched meteorite from the Gibeon cluster, Namibia. Credit: kevinzim / Kevin Walsh.{{free media}}
One of the Gibeon meteorites are on permanent display in Post Street Mall, Windhoek, Namibia. Credit: Moongateclimber.{{free media}}
Gibeon full slice is at the National Museum of Natural History, Washington D.C. Credit: Kinda Kinked.{{free media}}

The meteorite was discovered by the Nama people and used by them to make tools and weapons.

In 1836[103] the English captain J. E. Alexander collected samples of the meteorite in the vicinity of the Fish River, Nico farm, and sent them to London.[104] There John Herschel analyzed them and confirmed for the first time the extraterrestrial nature of the material.[104]

Between 1911 and 1913, 33 fragments of the meteorite were collected in the vicinity of Gibeon and brought to the capital Windhoek.[104] They weighed between 195 and 506 kilograms (430 and 1,116 lb) and were first stored, then displayed at Zoo Park as a single heap.[104] In 1975 a public fountain displaying the meteorite fragments was planned, the pieces were removed and stored at Alte Feste, where two of the fragments were stolen, the fountain was erected in Post Street Mall, with two empty pillars for the missing fragments, since then, two more fragments were removed from the fountain, so that it displays only 29 today.[104]

The fragments of the meteorite in the strewn field are dispersed over an elliptical area 390 kilometres (240 mi) long and 120 kilometres (75 mi) wide, with the core of this area situated near the village of Gibeon in Namibia's Hardap Region: about 100–150 different fragments have been collected over time, and additional pieces are found occasionally.[104]

  1. Type: Iron meteorite.
  2. Name: NICO, Gibeon.
  3. Group: IVA.[103]
  4. Structural classification: Fine octahedrite.
  5. Composition: 91.8% Fe; 7.7% Ni; 0.5% Co; 0.04% P; 2.4 ppm Ir; 1.97 ppm Ga; 0.111 ppm Ge.
  6. Country: Namibia.
  7. Region: Great Namaqualand.
  8. Coordinates 25°23' S 17°00'47" E.[103]
  9. Observed fall: No.[103]
  10. Fall date: prehistoric times.[103]
  11. Found date: 1836.[103]
  12. TKW: 26000 kg.[103]
  13. Strewn field: Yes.

IVB meteorites[edit | edit source]

  • IVB meteorite (IVB): Ataxites, 16–26% Ni, 0.17–0.27 ppm Ga, 0,03–0,07 ppm Ge, 13–38 ppm Ir, Ge-Ni correlation positive.

Chinga meteorites[edit | edit source]

Chinga exhibit is in the Naturhistorisches Museum Nürnberg - Nuremberg, Germany. Credit: Daderot.{{free media}}
This is a 700 g individual piece of the Chinga iron meteorite, approx. 9 centimeters wide, an ataxite. Credit: H. Raab.{{free media}}

Ataxites exhibit no Widmanstätten patterns upon etching.

Composition: Meteoric iron 82.8%, 16.7% Ni in very rare kamacite lamella, inclusions: daubréelite.[105] The total chemical composition is 82.8% iron, 16.6% nickel, and the rest mostly cobalt and phosphorus.[106]

Fragments of the meteorite were found in 1913 by gold diggers in Tuva near the Chinge River after which it is named. Eventually, Nikolay Chernevich, a mining engineer supervising the gold diggers, sent thirty pieces, the heaviest of which was 20.5 kilograms (45 lb), to the Russian Academy of Sciences in Saint Petersburg.[106] Later expeditions have retrieved about 250 pieces with a total mass of 209.4 kilograms (462 lb).[107]

No impact structure was found.[106] Studies from the fluvial deposits in which the meteorites were found estimate that it fell about 10,000 to 20,000 years ago. It burst during passage through the atmosphere, the pieces impacting on a glacier.

  1. Group: IVB-an, (2000), Iron-ung (2006).

Hoba meteorites[edit | edit source]

Hoba meteorite is the largest iron meteorite found on Earth and the largest piece of iron found on Earth. 19°35′32″S 17°56′01″E / 19.59222°S 17.93361°E / -19.59222; 17.93361. Credit: J. Engelbrecht.{{fairuse}}
The Hoba meteorite is shown in 2014 after becoming a tourist attraction. Credit: Sergio Conti from Montevecchia (LC), Italia.{{free media}}

The Hoba iron meteorite shown on the right left no observable crater. This meteorite is the largest meteorite ever found and the largest piece of iron ever found. It is specifically an ataxite, which contains a significant fraction of nickel (about 84% iron and 16% nickel, with traces of cobalt), but not in taenite. It was estimated to weigh 66 tons when initially discovered.

  1. An ataxite iron meteorite belonging to the nickel-rich chemical class IVB.

Ungrouped meteorites[edit | edit source]

  • Ungrouped meteorites. This is actually quite a large collection (about 15% of the total) of over 100 meteorites that do not fit into any of the larger classes above, and come from about 50 distinct parent bodies.

Staunton meteorites[edit | edit source]

Widmanstätten pattern is in the Staunton Meteorite, on display at the Smithsonian Museum of Natural History, Washington, DC. Credit: Jstuby.{{free media}}

The Staunton meteorite was found near Staunton, Virginia in the mid-19th century. Six pieces of nickel-iron were located over a period of some decades, with a total weight of 270 lb.[108]

Tamentit meteorites[edit | edit source]

The Tamentit Iron Meteorite weighs about 500 kg and is on display at Vulcania park in France. Credit: Ji-Elle.{{free media}}

The Tamentit Iron Meteorite was found in 1864 in the Sahara Desert, The Tamentit Meteorite, weighing half a ton, was discovered in the sands of the Algerian Sahara in 1864 near of Tamentit city and is currently on display at Parc Vulcania (Puy-de-Dôme), on loan from the Museum national d'Histoire naturelle de Paris.[109]

Iron alloy minerals[edit | edit source]

"Grain size varies from 98 to 530 lm with an average of *150 lm. Minor [elements] oxidation [from an iron–nickel–chromium–cobalt–phosphorus alloy] is evidenced by the presence of a light brown and blue surface layer composed of very fine-grained (<1 lm) crystals on the surface."[110] "[T]he oxidation of minor elements in metallic alloys in the early solar system" is indicated to possess at instances a blue surface layer.[110]

Kamacites[edit | edit source]

Kamacite, Nantan (Nandan) iron meteorites, Nandan County, Guangxi Zhuang Autonomous Region, China. Size: 4.8×3.0×2.8 cm. The Nantan irons, a witnessed fall in 1516, have a composition of 92.35% iron and 6.96% nickel. Credit: Robert M. Lavinsky.{{free media}}

Kamacite is an alpha-(Fe,Ni) alloy, major constituent of iron meteorites, with the proportion iron:nickel about 90:10; small quantities of other elements, such as cobalt, carbon, a metallic luster, gray color and no clear cleavage although the structure is isometric-hexoctahedral, density is around 8 g/cm³ and its hardness is 4 on the Mohs scale of mineral hardness, sometimes called balkeneisen.[111]

"The principle constituent of a typical octahedrite meteorite with about 92% iron and 7% nickel."[112]

  1. Empirical Formula: Fe
    0.9
    Ni
    0.1
    .[111]
  2. Common Impurities: Co,C,P,S.[112]

Taenites[edit | edit source]

Taenite (Fe,Ni) is a mineral alloy found naturally on Earth mostly in iron meteorites, with nickel proportions of 20% up to 65%, one of four known Fe-Ni meteorite minerals: taenite, kamacite, tetrataenite, and antitaenite, is opaque with a metallic grayish to white color, isometric-hexoctahedral structure, density around 8 g/cm³, hardness i5 to 5.5 on the Mohs scale of mineral hardness, magnetic, with a crystal lattice of c≈a= 3.582 Å ±0.002 Å.[113]

Tetrataenites[edit | edit source]

Tetrataenite is an ultra-rare, extraterrestrial iron nickel alloy, found only in meteorites. Credit: Robert M. Lavinsky.{{free media}}

"Tetrataenite is a native metal found in meteorites with the composition FeNi."[114]

It is one of the mineral phases found in meteoric iron.[115][116][117]

Antitaenites[edit | edit source]

Antitaenite is a meteoritic metal alloy mineral composed of iron and nickel, 20-40% Ni (and traces of other elements) that has a face centered cubic crystal structure that exists as a new mineral species occurring in both iron meteorites and in chondrites[118]

The pair of minerals antitaenite and taenite constitute the first example in nature of two minerals that have the same crystal structure (face centered cubic) and can have the same chemical composition (same proportions of Fe and Ni) - but differ in their electronic structures: taenite has a high magnetic moment whereas antitaenite has a low magnetic moment.[119] This difference arises from a high-magnetic-moment to low-magnetic-moment transition occurring in the Fe-Ni bi-metallic alloy series.[120]

Allabogdanites[edit | edit source]

Allabogdanite is a very rare phosphide mineral with formula (Fe,Ni)
2
P, found in 1994 in the Onello meteorite.[121][122] It was described for an occurrence in the Onello meteorite in the Onello River basin, Sakha Republic; Yakutia, Russia; associated with taenite, schreibersite, kamacite, graphite and awaruite.[122] It was named for Russian geologist Alla Bogdanova.[123]

In a June 2021 study, scientists reported the discovery of terrestrial allabogdanite in a sedimentary formation, located in the Negev desert of Israel, just southwest of the Dead Sea.[124]

Awaruites[edit | edit source]

Awaruite pebble is from Josephine Creek, Josephine Creek District, Josephine County, Oregon, USA. Credit: Robert M. Lavinsky.{{free media}}

Awaruite has the chemical formula Ni
2
Fe
.[125]

Awaruite occurs in river placer deposits derived from serpentinized peridotites and ophiolites, also occurs as a rare component of meteorites, in association with native gold and magnetite in placers; with copper, heazlewoodite, pentlandite, violarite, chromite, and millerite in peridotites; with kamacite, allabogdanite, schreibersite and graphite in meteorites.[126]

It was first described in 1885 for an occurrence along Gorge River, near Awarua Bay, South Island, New Zealand, its type locality.[126][127][128]

Awaruite is also known as josephinite in an occurrence in Josephine County, Oregon where it is found as placer nuggets in stream channels and masses in serpentinized portions of the Josephine peridotite. Some nuggets contain andradite garnet.[129]

Awaruite occur as an ore mineral in a large low grade deposit in central British Columbia, some 90 km northwest of Fort St. James, disseminated in the Mount Sidney Williams ultramafic/ophiolite complex.[130]

Reevesites[edit | edit source]

Yellow green crystal plates of the rare Ni mineral reevesite from Clear Creek (Clear Creek, Picacho Peak, New Idria, San Benito County, California, United States of America). Credit: David Hospital.{{free media}}

Chemical Formula: Ni
6
Fe3+
2
(CO
3
)(OH)
16
•4(H
2
O
).[131]

Environment: Alteration product of a highly weathered iron-nickel meteorite.[131]

Type Locality: Wolf Creek meteorite, found three km west of the Scotia talc mine, Bon Accord area, Barberton, Transvaal, South Africa.[131]

Crystal System: Trigonal.[132]

Member of the Hydrotalcite Group > Hydrotalcite Supergroup.[132]

Geological Setting: Nickel rich ore deposits.[132]

Geological Setting of Type Material: alteration product of a highly weathered iron-nickel meteorite.[132]

Associated Minerals at Type Locality: Goethite, Jarosite, Serpentine Subgroup, Apatite, Lipscombite.[132]

Schreibersites[edit | edit source]

Slice is from the Gebel Kamil Meteorite with schreibersite rimmed by kamacite. Credit: Butcherbird.{{free media}}

Schreibersite is generally a rare iron nickel phosphide mineral, (Fe,Ni)3P, though common in iron-nickel meteorites, where the only known occurrence of the mineral on Earth is located on Disko Island in Greenland.[133]

Another name used for the mineral is rhabdite that forms tetragonal crystals with perfect 001 cleavage; color ranges from bronze to brass yellow to silver white; density is 7.5 and a hardness of 6.5 – 7; opaque with a metallic luster and a dark gray streak; named after the Austrian scientist Carl Franz Anton Ritter von Schreibers (1775–1852), who was one of the first to describe it from iron meteorites.[134]

Schreibersite is reported from the Magura Meteorite, Arva-(present name – Orava), Slovak Republic; the Sikhote-Alin Meteorite in eastern Russia; the São Julião de Moreira Meteorite, Viana do Castelo, Portugal; the Gebel Kamil (meteorite) in Egypt; and numerous other locations including the Moon.[135]

Schreibersite and other meteoric phosphorus bearing minerals may be the ultimate source for the phosphorus that is so important for life on Earth.[136][137][138] Pyrophosphite is a possible precursor to pyrophosphate, the molecule associated with adenosine triphosphate (ATP), a co-enzyme central to energy metabolism in all life on Earth, produced by subjecting a sample of schreibersite to a warm, acidic environment typically found in association with volcanic activity, activity that was far more common on the primordial Earth, possibly representing "chemical life", a stage of evolution which may have led to the emergence of fully biological life as exists today.[139]

Carlsbergites[edit | edit source]

Agpalilik meteorite is outside the Geological Museum in Copenhagen. Credit: Michael B. H..{{free media}}

Carlsbergite was first described in the Agpalilik fragment of the Cape York meteorite.

It is a chromium nitride mineral (CrN),[140] named after the Carlsberg Foundation that backed the recovery of the Agpalilik fragment from the Cape York meteorite.[140]

It occurs in meteorites along the grain boundaries of kamacite or troilite in the form of tiny plates,[140] associated with kamacite, taenite, daubreelite, troilite and sphalerite.[141]

In addition to the Cape York meteorite, carlsbergite has been reported from:[142]

  • the North Chile meteorite in the Antofagasta Province, Chile
  • the Nentmannsdorf meteorite of Bahretal, Erzgebirge, Saxony
  • the Okinawa Trough, Senkaku Islands, Okinawa Prefecture, Japan
  • the Uwet meteorite of Cross River State, Nigeria
  • the Sikhote-Alin meteorite, Sikhote-Alin Mountains, Russia
  • the Hex River Mountains meteorite from the Cape Winelands District, Western Cape Province, South Africa
  • the Canyon Diablo meteorite of Meteor Crater, Coconino County, Arizona
  • the Smithonia meteorite of Oglethorpe County, Georgia
  • the Kenton County meteorite of Kenton County, Kentucky
  • the Lombard meteorite of Broadwater County, Montana
  • the Murphy meteorite of Cherokee County and the Lick Creek meteorite of Davidson County, North Carolina
  • the New Baltimore meteorite of Somerset County, Pennsylvania.

Osbornites[edit | edit source]

Osbornite is a very rare natural form of titanium nitride (TiN), found almost exclusively in meteorites.[143][144]

Silicon hydrogenated amorphous carbon alloys[edit | edit source]

"The broad, 60 < FWHM < 100 nm, featureless luminescence band known as extended red emission (ERE) is seen in such diverse dusty astrophysical environments as reflection nebulae17, planetary nebulae3, HII regions (Orion)12, a Nova11, Galactic cirrus14, a dark nebula7, Galaxies8,6 and the diffuse interstellar medium (ISM)4. The band is confined between 540-950 nm, but the wavelength of peak emission varies from environment to environment, even within a given object. ... the wavelength of peak emission is longer and the efficiency of the luminescence is lower, the harder and denser the illuminating radiation field is13. These general characteristics of ERE constrain the photoluminescence (PL) band and efficiency for laboratory analysis of dust analog materials."[145]

"The PL efficiencies measured for [hydrogenated amorphous carbon] HAC and Si-HAC alloys are consistent with dust estimates for reflection nebulae and planetary nebulae, but exhibit substantial photoluminescence below 540 nm which is not observed in astrophysical environments."[145]

"Optical constants measured at normal incidence for iron (Bolotin et al., 1969) and for iron-nickel alloys (Sasovskaya and Noskov, 1974) also predict a red-sloped spectrum."[146]

Carbonide minerals[edit | edit source]

The mineral Lonsdaleite is made from carbon with a different arrangement than diamond. Credit: payam.{{fairuse}}

"The mineral Lonsdaleite is a translucent, brownish yellow and is made from the atoms of carbon but the arrangement of these atoms is different from the arrangement of carbon atoms in a diamond. [...] The mineral is very rare and is formed naturally whenever [...] graphite containing meteorites fall on the earth and hit the surface."[147]

"Found in the Canyon Diablo and Goalpara meteorites."[148]

Def. any

  1. "binary compound of carbon and a more electropositive element",[149]
  2. the "polyatomic ion C2−
    2
    , or any of its salts",[150]
  3. the "monatomic ion C4−
    , or any of its salts",[150]
  4. a "carbon-containing alloy or doping of a metal or semiconductor, such as steel",[150]
  5. an "archaic form of carbide",[151] or a theoretical definition:
  6. "naturally occurring minerals composed of 50 atomic percent, or more, carbon"[152]

are called carbonides.

The second part of a theoretical definition:

Def. "minerals with greater than 25 at % carbon but less than 50 at % carbon"[153] are called carbonide-like minerals.

Brasses[edit | edit source]

The earliest brasses may have been natural alloys made by smelting zinc-rich copper ores.[154]

The compositions of these early "brass" objects are highly variable and most have zinc contents of between 5% and 15% wt which is lower than in brass produced by cementation.[154]

Metalloid minerals[edit | edit source]

This massive native arsenic with quartz and calcite is from Ste. Marie-aux-mines, Alsace, France. Credit: Aram Dulyan.{{free media}}

Metalloids are elements whose properties are intermediate between metals and solid nonmetals or semiconductors.

A variety of elements are often considered metalloids:

  1. boron, considered here in the boronides,
  2. aluminum, a face-centered cubic metal, considered in the aluminides,
  3. silicon, here in the siliconides,
  4. gallium (it can occur in the liquid state as a mineraloid),
  5. germanium,
  6. arsenic,
  7. selenium, also included in the chalcogens,
  8. indium,
  9. tin,
  10. antimony,
  11. tellurium, also included in the chalcogens,
  12. polonium, considered as among the heavy metals and
  13. astatine, here is with the halogens.

Stishovites[edit | edit source]

Stishovite is an extremely hard, dense tetragonal polymorph of silicon dioxide. It is very rare on the Earth's surface; however, it may be a predominant form of silicon dioxide in the Earth, especially in the lower mantle.[155]

Until recently, the only known occurrences of stishovite in nature formed at the very high shock pressures (>100 kbar, or 10 GPa) and temperatures (> 1200 °C) present during hypervelocity meteorite impact into quartz-bearing rock. Minute amounts of stishovite have been found within diamonds,[156] and post-stishovite phases were identified within ultra-high-pressure mantle rocks.[157] Stishovite may also be synthesized by duplicating these conditions in the laboratory, either isostatically or through shock (see shocked quartz).[158]

Minute amounts of stishovite has been found within diamonds.[156]

Troilites[edit | edit source]

Polished and etched surface of the Mundrabilla meteorite from Australia, where the darker brownish areas with striations are troilite with exolved daubréelite. Credit: Raymond T. Downward, NASA.{{free media}}

Troilite is a rare iron sulfide mineral with the simple formula of FeS. It is the iron-rich endmember of the pyrrhotite group. Pyrrhotite has the formula Fe(1-x)S (x = 0 to 0.2) which is iron deficient. As troilite lacks the iron deficiency which gives pyrrhotite its characteristic magnetism, troilite is non-magnetic.[159]

Troilite can be found as a native mineral on Earth but is more abundant in meteorites, in particular, those originating from the Moon and Mars. It is among the minerals found in samples of the Chelyabinsk meteor (the meteorite that struck Russia in Chelyabinsk on February 15th, 2013).[160] Uniform presence of troilite on the Moon and possibly on Mars has been confirmed by the Apollo, Viking and Phobos space probes. The relative intensities of isotopes of sulfur are rather constant in meteorites as compared to the Earth minerals, and therefore troilite from Canyon Diablo meteorite is chosen as the international sulfur isotope ratio standard, the Canyon Diablo Troilite (CDT).

Troilite has hexagonal structure (Pearson symbol hP24, Space group P-62c No 190). Its unit cell is approximately a combination of two vertically stacked basic NiAs-type cells of pyrrhotite, where the top cell is diagonally shifted.[161] For this reason, troilite is sometimes called pyrrhotite-2C.[162]

A meteorite fall was observed in 1766 at Albareto, Modena, Italy. Samples were collected and studied by Domenico Troili who described the iron sulfide inclusions in the meteorite. These iron sulfides were long considered to be pyrite (i.e., FeS
2
). In 1862, German [mineralogist Gustav Rose analyzed the material and recognizd it as stoichiometric 1:1 FeS andgave it the name troilite in recognition of the work of Domenico Troili.[163][159][164][165]

Troilite has been reported from a variety of meteorites occurring with daubréelite, chromite, sphalerite, graphite, and a variety of phosphate and silicate minerals.[163] It has also been reported from serpentinite in the Alta mine, Del Norte County, California and in layered igneous intrusions in Western Australia, the Ilimaussaq intrusion of southern Greenland, the Bushveld Complex in South Africa and at Nordfjellmark, Norway. In the South African and Australian occurrence it is associated with copper, nickel, platinum iron ore deposits occurring with pyrrhotite, pentlandite, mackinawite, cubanite, valleriite, chalcopyrite and pyrite.[163][166]

Troilite is extremely rarely encountered in the Earth's crust (even pyrrhotite is relatively rare compared to pyrite and Iron(II) sulfate minerals). Most troilite on Earth is of meteoritic origin. One iron meteorite, Mundrabilla contains 25 to 35 volume percent troilite.[167] The most famous troilite-containing meteorite is Canyon Diablo. Canyon Diablo Troilite (CDT) is used as a standard of relative concentration of different isotopes of sulfur.[168] Meteoritic standard was chosen because of the constancy of the sulfur isotopic ratio in meteorites, whereas the sulfur isotopic composition in Earth materials varies due to the bacterial activity. In particular, certain sulfate reducing bacteria can reduce 32
SO2−
4
1.07 times faster than 34
SO2−
4
, which may increase the 34
S
/32
S
ratio by up to 10%.[169]

Troilite is the most common sulfide mineral at the lunar surface. It forms about one percent of the lunar crust and is present in any rock or meteorite originating from moon. In particular, all basalts brought by the Apollo 11, Apollo 12, Apollo 15 and Apollo 16 missions contain about 1% of troilite.[161][170][171][172]

Troilite is regularly found in Martian meteorites, similar to the Moon's surface and meteorites, the fraction of troilite in Martian meteorites is close to 1%.[173][174]

Based on observations by the Voyager spacecraft in 1979 and Galileo in 1996, troilite might also be present in the rocks of Jupiter’s satellites Ganymede and Callisto.[159] Whereas experimental data for Jupiter's moons are yet very limited, the theoretical modeling assumes large percentage of troilite (~22.5%) in the core of those moons.[175]

  1. Category: Sulfide mineral.
  2. Formula: FeS.
  3. System: Hexagonal crystal system.
  4. Class: Ditrigonal dipyramidal (6m2)
    H-M symbol: (6m2).
  5. Symmetry: P62c.
  6. Unit cell: a = 5.958, c = 11.74 [Å]; Z = 12.
  7. Color: Pale gray brown.
  8. Habit: Massive, granular; nodular; platey to tabular.
  9. Cleavage: None.
  10. Fracture: Irregular.
  11. Mohs hardness: 3.5 - 4.0.
  12. Luster: Metallic.
  13. Streak: Gray black.
  14. Diaphaneity: Opaque.
  15. Gravity: 4.67–4.79.
  16. Alteration: Tarnishes on exposure to air.

Galliums[edit | edit source]

This is an example of gallite from Namibia. Credit: Hudson Institute of Mineralogy.{{fairuse}}

While native gallium would be the best source of gallium, it apparently does not occur on Earth.

Gallite (CuGaS2) is 25 at % gallium.

Germaniums[edit | edit source]

This sample of germanite is displayed in the Smithsonian Museum of Natural History. Credit: R Nave.{{fairuse}}

The sample of germanite on the right has a composition of Cu26Fe4Ge4S32. Generally, germanite has a composition closer to Cu3(Ge, Ga, Fe, Zn) (S,As)4.[148] "This sample also contains tennantite."[176]

Arsenics[edit | edit source]

Native arsenic such as this specimen is found in silver ore veins. Credit: Amethyst Galleries, Inc.{{fairuse}}

Native arsenic such as in the image on the right and at the top of this resource occurs in silver ore veins.

Allemontites[edit | edit source]

Allemontite (with Pen for scale) is from the mineral collection of Brigham Young University Department of Geology, Provo, Utah. Credit: Andrew Silver, USGS.{{free media}}
Allemontite specimen is from Příbram, Central Bohemia Region, Bohemia (Böhmen; Boehmen), Czech Republic. Credit: Robert Lavinsky.{{free media}}

Allemontite is a native alloy of arsenic and antimony, with a composition of AsSb.[148]

The first example on the right is from the mineral collection of Brigham Young University Department of Geology, Provo, Utah.

The second on the left is from Příbram, Central Bohemia Region, Bohemia (Böhmen; Boehmen), Czech Republic.

As a natural source of arsenic, it has 50 at % arsenic.

Seleniums[edit | edit source]

Selenium (native) with pen for scale is from the mineral collection of Brigham Young University Department of Geology, Provo, Utah. Credit: Andrew Silver, USGS.{{free media}}
The dark gray mineral in the yellow sandstone is native selenium. Credit: James St. John.{{free media}}

On the right is a photograph of native selenium from the mineral collection of Brigham Young University Department of Geology, Provo, Utah.

The second image on the left shows dark gray selenium in sandstone from Westwater Canyon Section 23 Mine Grants, New Mexico.

Indiums[edit | edit source]

These pieces of native indium are from Eastern Transbaikal, Russia. Credit: Michael Scott.{{fairuse}}

On the right are microprobe fragments of native indium from Eastern Transbaikal, Russia. The electron microprobe confirms that indium is the only component of the metallic phase.

Tins[edit | edit source]

This small piece of native tin is from the Badiko District, Bauchi State, Nigeria. Credit: Robert Lavinsky.{{free media}}
This is native tin from a porphyry copper deposit in the Bingham Deposit, Utah, USA. Credit: Alison Roberts.{{fairuse}}

Native tin such as in the images on the right and left occurs in two crystal forms: α-Sn (cubic) and β-Sn (tetragonal).[148]

Antimonies[edit | edit source]

This is massive antimony with oxidation products from Arechuybo, Mexico. Credit: Aram Dulyan at the Natural History Museum, London.{{free media}}
The native antimony crystals, lustrous and nicely striated in part, range up to 0.5 cm in size. Credit: Robert Lavinsky.{{free media}}

Native antimony such as occurs in the rock on the upper right with its various oxidation products is crystalline in the hexagonal system.

The second image on the left shows hexagonal crystals with metallic luster.

Telluriums[edit | edit source]

This is a native tellurium crystal from the Emperor Mine, Vatukoula, Tavua Gold Field, Viti Levu, Fiji. Credit: Robert Stravinsky.{{free media}}

On the right is an example of native tellurium from the Emperor Mine, Vatukoula, Tavua Gold Field, Viti Levu, Fiji.

Hypotheses[edit | edit source]

  1. The use of satellites should provide ten times the information as sounding rockets or balloons.

A control group for a radiation satellite would contain

  1. a radiation astronomy telescope,
  2. a two-way communication system,
  3. a positional locator,
  4. an orientation propulsion system, and
  5. power supplies and energy sources for all components.

A control group for radiation astronomy satellites may include an ideal or rigorously stable orbit so that the satellite observes the radiation at or to a much higher resolution than an Earth-based ground-level observatory is capable of.

See also[edit | edit source]

References[edit | edit source]

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