Metallic Nickel-iron Research Articles

Ni3 FeN-Supported Fe3 Pt Intermetallic Nanoalloy as a High-Performance Bifunctional Catalyst for Metal-Air Batteries.

Electrocatalysts for both the oxygen reduction and evolution reactions (ORR and OER) are vital for the performances of rechargeable metal-air batteries. Herein, we report an advanced bifunctional oxygen electrocatalyst consisting of porous metallic nickel-iron nitride (Ni3 FeN) supporting ordered Fe3 Pt intermetallic nanoalloy. In this hybrid catalyst, the bimetallic nitride Ni3 FeN mainly contributes to the high activity for the OER while the ordered Fe3 Pt nanoalloy contributes to the excellent activity for the ORR. Robust Ni3 FeN-supported Fe3 Pt catalysts show superior catalytic performance to the state-of-the-art ORR catalyst (Pt/C) and OER catalyst (Ir/C). The Fe3 Pt/Ni3 FeN bifunctional catalyst enables Zn-air batteries to achieve a long-term cycling performance of over 480 h at 10 mA cm-2 with high efficiency. The extraordinarily high performance of the Fe3 Pt/Ni3 FeN bifunctional catalyst makes it a very promising air cathode in alkaline electrolyte.

Magnetic and electrical characterization of nickel-rich NiFe thin films synthesized by atomic layer deposition and subsequent thermal reduction

Nickel-rich NiFe thin films (Ni92Fe8, Ni89Fe11 and Ni83Fe17) were prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. In order to obtain NixFe1−xOy films, one ALD supercycle was performed according to the following sequence: m NiCp2/O3, with m = 1, 2 or 3, followed by one FeCp2/O3 cycle. The supercycle was repeated n times. The thermal reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. The metallic nickel iron alloy thin films were investigated and characterized with respect to crystallinity, morphology, resistivity, and magnetism. As proof-of-concept magnetic properties of an array of Ni83Fe17, close to the perfect Permalloy stoichiometry, nanotubes and an isolated tube were investigated.

Facile Synthesis of Nickel–Iron/Nanocarbon Hybrids as Advanced Electrocatalysts for Efficient Water Splitting

Developing active, stable, and low-cost electrocatalysts which can promote the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the same electrolyte is undoubtedly a vital progress toward a hydrogen economy. Herein, we report that such electrocatalysts can be easily prepared by pyrolyzing a precursor composed of nickel and iron salts with urea under inert atmospheres without any post-treatments. The obtained products are composed of metallic nickel–iron alloy nanoparticles either encapsulated in or dispersed on nitrogen-doped bamboo-like carbon nanotubes (CNTs). This simple synthesis route could simultaneously realize nanostructuring, doping, and hybridizing with nanocarbon, which have been demonstrated as efficient strategies to optimize the catalytic activity of an electrocatalyst. The in situ formed hybrid catalysts exhibit good catalytic performances for both OER and HER under alkaline conditions, and the doping content of iron significantly affects the activities. When the bes...

Phase change in subducted lithosphere, impulse, and quantizing Earth surface deformations

Abstract. The new paradigm of plate tectonics began in 1960 with Harry H. Hess's 1960 realization that new ocean floor was being created today and is not everywhere of Precambrian age as previously thought. In the following decades an unprecedented coming together of bathymetric, topographic, magnetic, gravity, seismicity, seismic profiling data occurred, all supporting and building upon the concept of plate tectonics. Most investigators accepted the premise that there was no net torque amongst the plates. Bowin (2010) demonstrated that plates accelerated and decelerated at rates 10−8 times smaller than plate velocities, and that globally angular momentum is conserved by plate tectonic motions, but few appeared to note its existence. Here we first summarize how we separate where different mass sources may lie within the Earth and how we can estimate their mass. The Earth's greatest mass anomalies arise from topography of the boundary between the metallic nickel–iron core and the silicate mantle that dominate the Earth's spherical harmonic degree 2 and 3 potential field coefficients, and overwhelm all other internal mass anomalies. The mass anomalies due to phase changes in olivine and pyroxene in subducted lithosphere are hidden within the spherical harmonic degree 4–10 packet, and are an order of magnitude smaller than those from the core–mantle boundary. Then we explore the geometry of the Emperor and Hawaiian seamount chains and the 60° bend between them that aids in documenting the slow acceleration during both the Pacific Plate's northward motion that formed the Emperor seamount chain and its westward motion that formed the Hawaiian seamount chain, but it decelerated at the time of the bend (46 Myr). Although the 60° change in direction of the Pacific Plate at of the bend, there appears to have been nary a pause in a passive spreading history for the North Atlantic Plate, for example. This, too, supports phase change being the single driver for plate tectonics and conservation of angular momentum. Since mountain building we now know results from changes in momentum, we have calculated an experimental deformation index value (1–1000) based on a world topographic grid at 5 arcmin spacing and displayed those results for viewing.

The effect of irradiation on the magnetic properties of rock and synthetic samples: Implications to irradiation of extraterrestrial materials in space

We report here the results of laboratory analog experiments to consider the potential effects of solar energetic particles (SEP or solar-flare-associated particles) and galactic cosmic rays (GCR) on the magnetic properties of extraterrestrial materials. We carried out proton bombardment experiments (with irradiation energies E1=400, E2 =850 keV and three irradiation fluences in 1014–1016p/cm2 range) and lead-ion bombardment experiments (E =1 GeV) on (previously demagnetized by 120 mT alternating magnetic field) rock and synthetic samples with the following magnetic carriers: metallic iron and nickel iron, Ti-rich and Ti-free magnetite, pyrrhotite. Irradiation experiments resulted in either further demagnetization or magnetization of irradiated samples depending on the type of magnetic mineralogy and type of ionizing radiation involved. Apart for the formation of radiation-induced remanent magnetization (RIRM), we observed major changes in bulk magnetic properties, i.e., a moderate to dramatic decrease (up to 93%) in the coercivity of remanence Bcr for all iron-bearing phases (iron-in-epoxy and Bensour meteorite samples). Contrary to iron-bearing samples, several magnetite-bearing samples experienced a radiation-induced magnetic hardening (increase in Bcr). Magnetic hardening was also observed for Ar2+ ion-irradiated nickel iron-bearing HED meteorites, measured for comparison with the previously stated results. Therefore, the combined effect of SEP with GCR may magnetically soften iron-bearing materials and harden magnetite-bearing materials. In order to answer the question wether RIRM may account for natural remanent magnetization of meteorites and lunar samples, physical mechanism of RIRM formation and potential dependence of RIRM intensity on the background magnetic field present during irradiation event should be investigated.

Rb–Sr isotopic systematics of alkali-rich fragments in the Yamato-74442 LL-chondritic breccia

We have undertaken mineralogical, petrographical and Rb–Sr isotopic studies on alkali-rich igneous rock fragments in the Yamato (Y)-74442 LL-chondritic breccia. The fragments are a few mm in size and are composed mainly of porphyritic olivine and dendritic pyroxene set in alkali-rich groundmass glass. Minor phases include chromite, troilite and metallic nickel–iron. Bulk chemical compositions of the fragments are almost identical to the host chondrite except for a depletion of sodium and an enrichment of potassium. Isotopic analyses of nine fragments from Y-74442 yield a Rb–Sr age of 4429±54Ma (2σ) for λ(87Rb)=0.01402Ga−1 with an initial ratio of 87Sr/86Sr=0.7144±0.0094 (2σ). Assuming precursors of the fragments formed 4568Ma with 87Sr/86Sr=0.69889 when the Solar System formed, a time-averaged Rb/Sr (weight) ratio of the source material for the fragments is calculated to be 2.58+0.91/−0.93.The extremely high Rb/Sr value of this source is difficult to interpret by any igneous fractionation or liquid immiscibility, but can be explained by mixing of a chondritic component with an alkali-rich component formed in the early solar nebula. In our preferred model, the alkali component with Rb/Sr⪢30 would have condensed from the residual nebular gas after removal of refractory strontium and must have been isolated for a long time in a region where the temperature was sufficiently low to prevent reaction with other silicates/oxides. A mixture of the alkali component (early nebular condensates) and the ferromagnesian component could reflect flash heating induced by impact on an LL-chondritic parent body at least 4429Ma ago, and further enrichments of rubidium and potassium relative to strontium could have occurred during this event. The resulting impact-melt rocks could have been fragmented by later impact event(s) and finally incorporated into the Y-74442 parent body. Thus, a remarkable signature of alkali enrichments both in the early solar nebula and later on the LL-chondrite parent body is preserved as a minor component of some chondritic breccias such as Y-74442.

U-Pb isotope systematics in josephinites and associated rocks

Josephinite nodules are composed of metallic nickel iron alloy intergrown with andradite garnet. They are found in the peridotitic section of an obducted ophiolite in SW Oregon. The origin of josephinite is widely debated: for example, previous investigation have proposed it as a byproduct of low temperature synserpentinization processes linked to the intrusion of dikes or and its derivation from primitive mantle, conceivably from as deep as the core mantle boundary. We report U-Pb data from josephinites, wyrdite (a rock associated with josephinite) consisting of rutile and ilmenite intergrown with silicates, and their surrounding rocks (hornblende diorites and harzburgites). The measured Pb isotopic composition of all decontaminated, leached josephinite metal samples plots in the Pb-Pb diagram just above/in the MORB field, while the first leachates are characterized by higher 207 Pb/ 204 Pb ratios. The isotopic Pb composition measured in the leachates of the wyrdite defines a line whose slope corresponds to an age of 159 ± 8 Myr. The harzburgites show a wide spread in Pb isotopic compositions; all samples lie above the MORB field and three samples plot to the left side of the 4.55 AE geochron. The hornblende diorite dikes, characterized by the highest U and Pb concentrations of all studied rocks, plot in the MORB field. None of these different rocks is characterized by a single or homogeneous Pb composition. All samples are affected by secondary alteration processes: the circulation of hydrothermal fluids disturbed the dikes and ultramafic rocks and serpentinization processes have affected harzburgites, josephinites, and wyrdites. Thus the Pb isotopic composition measured today represents a mixture of initial Pb, radiogenic Pb and inherited Pb in variable proportions. Concerning the origin of josephinite these results show a close relationship between josephinite, wyrdite, and the dikes; e.g.: (1) the Pb-Pb age of wyrdite is identical to that of the dikes; (2) the Pb isotopic composition of the decontaminated josephinite metal is close to that of the dikes.

A 3.6-b.y.-old impact-melt rock fragment in the plainview chondrite: Implications for the age of the H-group chondrite parent body regolith formation

Major, minor, trace and REE abundances as well as mineralogical and textural properties of a light-colored, poikilitic, metallic nickel-iron- and troilite-poor lithic fragment in the brecciated Plainview, Texas, H5 chondrite unambiguously show that the fragment is of H-group chondrite parentage, despite its non-chondritic texture and appearance. 40Ar- 39Ar age dating indicates that the fragment is 3.63 b.y. old, whereas the Plainview host chondrite is 4.4 b.y. old. The fragment's texture and certain mineral compositions, such as relatively high CaO in olivine and orthopyroxene, the presence of alkali-rich feldspar and interstitial material, and metallic nickel-iron of Ni contents of 10–15 wt.% (martensite), indicate that the fragment formed by relatively fast cooling from a melt. We propose that the fragment crystallized from an impact-produced melt of H-group chondrite parentage (similar in composition to the Plainview host material) from which substantial metallic nickel-iron and troilite separated in the impact-melting process. Fragments of this rock, together with unequilibrated mineral and carbonaceous chondrite lithic fragments, were later impact-implanted into the regolith on the surface of the Plainview H5 group chondrite parent body not longer than 3.63 b.y. ago. This regolith, now represented by the Plainview chondrite, must have been in existence until at least 3.63 b.y. ago, when the lithic fragment formed. Of course, assemblage of host chondrite and lithic fragment in the regolith could have taken place even more recently and, thus, the age of the Plainview parent body regolith may even be younger than 3.63 b.y.

Origin of josephinite.

Josephinite is a nickel-iron alloy-bearing rock from Josephine County, southwestern Oregon. Josephinite had been thought to be the same as the metallic nickel-iron mineral awaruite (KRISHNARAO, 1962, 1964; RAMDOHR, 1950), but recently it has been shown to be a complex assemblage of minerals (BIRD and WEATHERS, 1975a). Although most samples of josephinite are somewhat altered, least-altered josephinite consists of several nickel-iron alloys, one intergrown with andradite garnet, an iron-cobalt alloy, and minor amounts of iron-nickel arsenides, iron-nickel-copper sulphides, and various unidentified phases. The intergrown metal-garent assemblage is apparently unique to josephinite. Alteration phases include serpentine minerals and magnetite. Josephinite occurs as detritus in several streams that originate and flow on the Josephine Peridotite; bedrock includes sheared serpentinite zones and basaltic to dioritic dikes within the peridotite. It is a reasonable assumption that the josephinite pebbles must be associated with one or more of these rocks; however, no unequivocal, large josephinite samples have been found within bedrock. BIRD and WEATHERS (1975a) proposed that because of its remarkable and apparently unique composition and textures, and its association with obducted mantle, josephinite has been derived from the mantle, conceivably the deep-mantle. Subsequently, DICK (1974), THORNBER and HAGGERTY (1976) and BOTTO and MORRISON (1976), following RAMDOHR (1950), argued that josephinite was formed by reduction of silicates, or sulphides, during serpentinization of the Josephine Peridotite. Currently, there are two views concerning the origin of josephinite: 1) josephinite is a product of low-temperature, synserpentinization processes and is comparable with awaruite 2) because of its mineral composition, textures, and rock associations, josephinite pre-dated serpentinization of the Josephine Peridotite (obducted ophiolite), was related to the origin of the Josephine Peridotite, and was derived from the primitive mantle, conceivably from as deep as the core-mantle boundary. Excesses of 3He, 21Ne and 129Xe have recently been found in josephinite and have been interpreted to indicate a mantle residence and, perhaps, a primordial age for this rock (DOWNING et al., 1977; BOCHSLER et al., 1978). We continue to propose a mantle derivation of josephinite; additionally, we suggest that josephinite was primitive material incorporated into the earth during earth accretion.

Asteroid surface materials: Mineralogical characterizations from reflectance spectra

The interpretation of diagnostic parameters in the spectral reflectance data for asteroids provides a means of characterizing the mineralogy and petrology of asteroid surface materials. An interpretive technique based on a quantitative understanding of the functional relationship between the optical properties of a mineral assemblage and its mineralogy, petrology and chemistry can provide a considerably more sophisticated characterization of a surface material than any matching or classification technique for those objects bright enough to allow spectral reflectance measurements. Albedos derived from radiometry and polarization data for individual asteroids can be used with spectral data to establish the spectral albedo, to define the optical density of the surface material and, in general, to constrain mineralogical interpretations. Mineral assemblages analogous to most meteorite types, with the exception of ordinary chondritic assemblages, have been found as surface materials of Main Belt asteroids. C1- and C2-like assemblages (unleached, oxidized meteoritic clay minerals plus opaques such as carbon) dominate the population (∼80%) throughout the Belt, especially in the outer Belt. A smaller population of asteroids exhibit surface materials similar to C3 (CO, CV) meteoritic assemblages (olivine plus opaque, probably carbon) and are also distributed throughout the Belt. The relative size (diameter) distributions for these two populations of objects are consistent with an origin by sequential accretion from a cooling nebula (‘C2’ as surface layers, ‘C3’ as interior layers or cores). Based on information from meteoritic analogues and on qualitative models for the behavior of these materials during a heating episode, it seems unlikely that these ‘C2’- and ‘C3’-like asteroidal bodies have experienced any significant post-accretionary heating event either near surface or in the deep interior. The majority of remaining studied asteroids (20) of 65 asteroids exhibit spectral reflectance curves dominated by the presence of metallic nickel-iron in their surface materials. These objects are most probably the several end products of an intense thermal event leading to the melting and differentiating of their protobodies. These thermalized bodies are concentrated toward the inner part of the Asteroid Belt but exist throughout the Belt. The size of the proto-asteroid has apparently exercised control over the post-accretionary thermal history of these bodies. The available evidence indicates that all asteroids larger than about 450 km in (present) diameter have undergone a significant heating episode since their formation. The post-accretionary thermal history of the asteroidal parent bodies was apparently affected by both distance from the Sun and body size. The C2-like materials which dominate the main asteroid belt population appear to be relatively rare on earth-approaching asteroids. This suggests that most of these Apollo-Amor objects are not randomly derived from the main belt, but (a) may derive from a single event in recent time (∼107 yr), (b) may derive from a favorably situated source body, (c) may derive from a particular, compositionally anomalous region of the belt, or (d) may derive from an alternate source (e.g. comets).

STUDIES OF BRAZILIAN METEORITES V. EVIDENCE FOR SHOCK METAMORPHISM IN THE PARANAÍBA, MATO GROSSO, CHONDRITE

Mineral compositions, particularly of olivine (Fa 23.7 ), orthopyroxene (Fs 20.7 ), and chromite, and the bulk composition, especially the ratios Fe o /Ni o (5.05), Fe total /SiO 2 (0.52), and Fe o / /Fe total (0.31) and the contents of Fe total (20.86%) and metallic nickel-iron (7.92%), indicate that Paranaiba is an L-group chondrite. Homogeneous and uniform ferromagnesian minerals, scarcity of chondrules, and high degree of recrystallization suggest that it belongs to the petrologic class L6. Dark veins and areas formed by extensive shock alteration (>430 kilobars, 1500-1 700oC) with the angular to subrounded and rounded light fragments representing less altered portions of the original rock (-200 kilobars, <900oC). Light portions contain maskelvnite and, in the dark veins, olivine and pyroxene were shock-transformed into isotropic to weakly anisotropic grains ofessentially unaltered composition. Pressure gradients were high, even on a micron scale. Isotropic olivine is not ringwoodite, probably because the high temperature prohibited quench to preserve ringwoodite.

STUDIES OF BRAZILIAN METEORITES V. EVIDENCE FOR SHOCK METAMORPHISM IN THE PARANAÍBA, MATO GROSSO, CHONDRITE

Mineral compositions, particularly of olivine (Fa 23.7 ), orthopyroxene (Fs 20.7 ), and chromite, and the bulk composition, especially the ratios Fe o /Ni o (5.05), Fe total /SiO 2 (0.52), and Fe o / /Fe total (0.31) and the contents of Fe total (20.86%) and metallic nickel-iron (7.92%), indicate that Paranaîba is an L-group chondrite. Homogeneous and uniform ferromagnesian minerals, scarcity of chondrules, and high degree of recrystallization suggest that it belongs to the petrologic class L6. Dark veins and areas formed by extensive shock alteration (&gt;430 kilobars, 1500-1 700ºC) with the angular to subrounded and rounded light fragments representing less altered portions of the original rock (-200 kilobars, &lt;900ºC). Light portions contain maskelvnite and, in the dark veins, olivine and pyroxene were shock-transformed into isotropic to weakly anisotropic grains ofessentially unaltered composition. Pressure gradients were high, even on a micron scale. Isotropic olivine is not ringwoodite, probably because the high temperature prohibited quench to preserve ringwoodite.

The deficiency of siderophile elements in the Moon

The deficiency of siderophiles in the crust of the Earth is customarily attributed to leaching by metallic nickel-iron, which eventually sank to form the core. A similar deficiency exists in the Moon, which has, at best, a very much smaller core. Hence it is logical to consider the hypothesis that the Moon formed from the mantle of the Earth, after the siderophiles had been removed. It is shown that the non-hydrostatic figure of the Moon, and the requirement that the mascons must be supported, together with the high heat-flow, imply that the metal of the Moon is collected in the core. It probably amounts to less than 1 % of the Moon’s mass. Calculations show that if the core is in chemical equilibrium with the lunar silicates, then the nickel has been removed from the Moon as a whole to an extent which is greater than can be explained by theories of direct formation from a nebula. The only salvation for the idea of direct formation from a nebula appears to be an efficient process of extraction of the siderophiles by successive passage of small amounts of reduced metal through the silicate portion of the Moon. Since natural processes do not usually operate with the required efficiency, it can be concluded that the formation of the Moon by the fission of the Earth is geochemically plausible.

Minor element abundances in olivines of the Sharps (H-3) chondrite

Olivine crystals in 21 chondrules from the Sharps (H-3) chondrite were analyzed for CaO, Al2O3, Cr2O3, MnO, TiO2, NiO, and Na2O. The chondrules studied include representatives of all major types found in Sharps, and the mean fayalite contents of their olivine range from 1 to 28 %. Those olivines which contain less than 18 mol.% fayalite typically contain or occur with metallic nickel-iron; the others are metal-free.

Luna 16: An opaque mineral study and a systematic examination of compositional variations of spinels from Mare Fecunditatis

Opaque minerals identified by reflection microscopy and electron microprobe include ilmenite, members of the chromite-pichrochromite-hercynite-ulvospinel series, rutile, troilite, metallic iron and metallic nickel-iron alloys. Spinel compositions indicate an extensive but incomplete solid solution series between FeCr 2O 4-FeAl 2O 4 and Fe 2TiO 4. Members of this series are common to samples from each of the Apollo landing sites but the Luna 16 spinels are characterized by High Al (15–25% Al 2O 3), high Mg (4–9% MgO) contents, by compositions intermediate between (FeCr 2O 4-FeAl 2O 4)-Fe 2TiO 4 typical of Apollo 11, and by considerable variation of Cr/Al as a function of Fe/Mg not previously observed. The ratios Cr/Al and Fe/Mg show maximum variability in low-Ti chromites whereas intermediate titanian-chromites and chromian-ulvospinels show less variation of Cr/Al, and Fe/Mg is constant and high (⋍0.97). Ilmenite contains between 0.1 and 5.7 wt.% MgO; high geikielite contents and contrasting coexisting ilmenite textures (skeletal and phenocrystic) suggest possible reaction of early formed armalcolite with liquid. Shock deformation of ilmenite gives rise to simple lamellar twins in low intensity shocked fragments; complexly deformed twins and evidence of shock-induced melting are present in highly shocked fragments; and peripheral annealing of preexisting twin lamellae, associated with partial melting, is recorded for the first time in lunar ilmenite.

The mineralogy and petrology of chondritic meteorites

Chondritic meteorites are naturally divided into five chemical groups according to their chemical compositions. Within each group a range of textures exists which is generally interpreted as representing progressive degrees of recrystallization, although there are also significant primary variations in each group. In most chondrites the major minerals are olivine, orthopyroxene, albitic feldspar, troilite, calcic pyroxene, and metallic nickel-iron; the compositions of the silicate minerals are usually uniform within recrystallized chondrites and very similar for individual chondrites belonging to a given group. In unrecrystallized chondrites the minerals are usually quite variable in composition and the primary structures of individual chondrules are well preserved. Most of the properties of chondrites can be interpreted in terms of metamorphic equilibration and recrystallization of primary chondritic matter, although alternative hypotheses exist.

Rhenium and osmium abundances in chondritic meteorites

The abundances of Re and Os in thirty-two chondrites representing all classes have been determined by neutron activation analysis. Some disagreement with previous determinations of Os in ordinary chondrites can be explained by the difficulties of sampling for siderophilic elements when metallic nickel-iron is present. Considerable fractionation of Re and Os between chondrite classes is apparent, and cannot be interpreted solely on the basis of transfer of metallic phase rich in these two elements. Solar atomic abundances relative to 10 6 atoms Si calculated from the mean of all chondrites analysed are 0.053 atoms Re and 0.61 atoms Os.

The iron, magnesium, and calcium distribution in coexisting olivines and rhombic pyroxenes of chondrites

Iron, magnesium, and calcium in olivines and pyroxenes of 95 chondritic meteorites were analyzed with an electron microprobe. Of these, 86 were ‘Ordinary’ chondrites, each having constant iron-magnesium ratios in olivine and pyroxene. Between different meteorites these ratios vary within three narrow ranges which reflect the H- and L-group chondrites, as well as a third group, designated the LL group. The ratio of iron in olivine to that in coexisting pyroxene is nearly constant (∼1.1), particularly within the groups mentioned. A classification of stony meteorites based on the amount of iron in silicates and metal is proposed. It is shown that the iron content in the silicates is not related to the degree of metamorphism (recrystallization), and that therefore, the composition of the silicates was essentially established when the chondrules were formed. The ferrous iron also is not strictly related to the amount of metallic nickel-iron. Thus Prior's rule is not valid in its original sense, although it can be applied qualitatively when comparing the different groups of chondrites. The coexisting olivines and pyroxenes may not be in equilibrium in spite of their constant composition and the constant ratio between their iron contents. Furthermore, the metallic nickel-iron seems to have originated in the same melt as did the silicates.

Electron microprobe analysis of some rare minerals in the Norton County achondrite

The composition of the minerals constituting the Norton County achondrite has been ascertained by measuring a large number of individual grains of each mineral, using electron microprobe techniques. The following minerals were found: enstatite, forsterite, metallic nickel-iron, metallic copper, daubreelite, troilite, and two new species, titanoan troilite and ferromagnesian alabandite. The unusual association of minerals indicates that at the time when this meteorite was formed the environment was strongly reducing, and any hypothesis on the origin of meteorites based on comparison with terrestrial rock-forming mechanism must take this into account.

On the phase composition of meteorites

Seventy-three chondrites were examined. Their content of metallic nickel-iron, troilite, chromite, and silicate was determined quantitatively by planimetric integration of polished sections with an integration ocular, type 1. More than 300 large polished sections were measured, constituting a total area of 3700 cm2. In part, the results deviate markedly from the chemical analyses given in the literature. This deviation may be due to the use of too small samples in the earlier analyses. It was found that chondrites with more than 13 weight percent of metallic nickel-iron belong to the H group; those with less than 13 weight percent belong to the L group (exceptions to this rule are the carbonaceous chondrites). The average composition calculated from the individual results is: 11.0 percent metallic nickel-iron; 5.3 percent troilite; 0.25 percent chromite; 83.4 percent silicate (percent by weight). Because of the obviously inefficient sampling of cosmic matter by the earth, neither statistics of the weight nor frequency of meteorite falls can serve to calculate the average phase composition of the total meteoritic material.