Showing papers on "Magnetite published in 1978"
TL;DR: The magnetite particles were present in a range of sizes and morphologies as mentioned in this paper, and the incorporation of small amounts (2+ and its ability to exhibit the Jahn-Teller effect and the larger ionic radii of Mn 2+ and Cd 2+ may be responsible for their non-uniform distribution in the magnetite crystals.
125 citations
TL;DR: The magnetic properties of fresh and metamorphosed gabbros appeared to be similar as discussed by the authors, and the majority of the samples were characterized by median destructive fields greater than 200 Oe.
Abstract: Summary. Magnetic property studies (natural remanent magnetization, initial susceptibility, progressive alternating field demagnetization and magnetic mineralogy of selected samples) were completed on 45 samples of gabbro and metagabbro recovered from 14 North Atlantic ocean-floor localities. The samples are medium to coarse-grained gabbro and metagabbro which exhibit subophitic intergranular to hypidiomorphic granular igneous textures. The igneous mineralogy is characterized by abundant plagioclase, varying amounts of clinopyroxene and hornblende, and lesser amounts of magnetite, ilmenite and sphene. Metamorphic minerals (actinolite, chlorite, epidote and fine-grained alteration products) occur in varying amounts as replacement products or vein material. The opaque mineralogy is dominated by magnetite and ilmenite. The magnetite typically exhibits a trellis of exsolution-oxidation ilmenite lamellae that appears to have formed during deuteric alteration. The NRM intensities of the gabbros range over three orders of magnitude and give a geometric mean of 2.8 x 10-4gau~~ and an arithmetic mean of 8.8 x 10-4gauss. The Konigsberger ratio, a measure of the relative importance of remanent to induce magnetization, is greater than unity for the majority of the samples and indicates that remanent magnetization on average dominates the total magnetization of oceanic gabbros in the Earth's magnetic field. The magnetic properties of fresh and metamorphosed gabbros appeared to be similar. The majority of gabbros studied were characterized by median destructive fields greater than 200 Oe. The high stability is attributed largely to the effective subdivision of the magnetite grains by the
112 citations
TL;DR: In this article, it is proposed that these anomalies may arise from partially serpentinized ultramafic bodies which have metal alloys as the prime magnetic source material with Curie temperatures in the range 620°-1100°C.
Abstract: Ferrimagnetic minerals above their respective Curie temperatures are paramagnetic. Deep crustal magnetic anomalies are constrained, therefore, to a depth detection limit which is defined by the Curie isotherm. Although magnetite, with a Curie temperature of 580°C, is widely employed to map Curie isothermal surfaces it is a relatively rare mineral as stoichiometric Fe3O4. Solid solution of magnetite towards antiferromagnetic ulvospinel (Fe2TiO4) reduces the Curie temperature to a minimum of −153°C and a high order of ferrimagnetic behavior can only be accomplished in plutonic rocks under the most exacting conditions of equilibrium exsolution and oxidation. Magnetic anomaly models need not be constrained by the 580°C limit because the range in temperatures may vary between 300°C if maghemite (αFe2O3)dominates and 680°C if hematite (γFe2O3) is dominant. Because many magnetic anomaly interpretations require Curie isothermal depths in excess of 580°C, and because these may extend to the lower crust-upper mantle boundary, it is proposed that these anomalies may arise from partially serpentinized ultramafic bodies which have metal alloys as the prime magnetic source material with Curie temperatures in the range 620°-1100°C.
104 citations
TL;DR: In this article, the solubility of the univariant assemblage pyrite + pyrrhotite + magnetite has been determined in vapor saturated hydrothermal solutions from 200 to 350°C for NaCl concentrations ranging from 0.0 to 5.0 molal.
93 citations
Journal Article•
75 citations
TL;DR: In this article, the oxidation of magnetite yields the lacunar phase γ-Fe 2 O 3, for sizes less than 5000 A, and the rhombohedral phase, α-Fe 3 O 3 for sizes above 10 000 A.
67 citations
64 citations
TL;DR: In this article, the Boltzmann-Matano method was used to calculate the interdiffusion coefficient between Fe3O4 and Fe2.8Ti0.2O4 powder.
61 citations
TL;DR: In this paper, high quality equiaxed magnetite (Fe 3 O 4 ) crystals, up to 2 cm in extension, have been grown in a skull melter in an atmosphere of CO 2 by slow lowering of the crucible out of the stationary work coil.
51 citations
TL;DR: Magnetite/liquid distribution coefficients have been calculated that are consistent with observed variations in contents of V, Sc, Cr, and Ti in lavas from Craters of the Moon lava field, Idaho.
Abstract: Magnetite/liquid distribution coefficients have been calculated that are consistent with observed variations in contents of V, Sc, Cr, and Ti in lavas from Craters of the Moon lava field, Idaho. In particular, our average distribution coefficient for V (27±8) is in close agreement with that determined experimentally at the temperature and oxygen fugacity appropriate for crystallization of these lavas. Although this value is not very precise, it shows that V contents of at least some calcalkaline series are consistent with generation of andesitic and related magmas from basaltic parental magmas by crystal fractionation, involving removal of appreciable amounts of magnetite.
48 citations
TL;DR: In this article, a series of Li + + + ∼ Cs + has been established for the sorption capacities of transition metal ions: Cu 2+ > Zn 2 + > Ni 2+> Mn 2+ has also been established.
TL;DR: In this paper, it was shown that a thin layer of magnetite is sometimes observed in the scales of hot-rolled sheets and wire rods at the scale-metal interface and that this layer is produced, during the cooling of the products, by the wustite decomposition.
Abstract: A thin layer of magnetite is sometimes observed in the scales of hot-rolled sheets and wire rod at the scale-metal interface. The results of this study show that this layer of magnetite is produced, during the cooling of the products, by the wustite decomposition. The time/temperature field in which it appears has been defined. This inner layer is composed of pure magnetite, in epitaxy with the neighboring wustite, and the metal surface is not essential to its nucleation. The proeutectoīd reaction which, during cooling, produces an increase in the oxygen concentration of the wustite in contact with the metal favors the subsequent growth of the magnetite layer.
TL;DR: Anhysteretic remanent magnetization (DC field = 1 Oe, peak AC field = 1000 Oe) was given to an artificial sediment consisting of a kaolinite matrix and a 0.03% magnetic fraction of needle-shaped magnetite grains as discussed by the authors.
Patent•
12 Jun 1978TL;DR: In this article, the instant invention relates to the production of glass and glass-ceramic compositions containing a ferrimagnetic crystal phase throughout which respond thermally to fields generated by induction coils.
Abstract: The instant invention relates to the production of glass and glass-ceramic compositions containing a ferrimagnetic crystal phase throughout which respond thermally to fields generated by induction coils. Magnetite (Fe3 O4) is the preferred ferrimagnetic crystal phase because of its high permeability and low resistivity (˜10-4 ohm-cm) at room temperature as well as the relative low cost of iron when compared with other ferrimagnetic species. Two general composition areas are of interest: Na2 O and/or K2 O-FeO-B2 O3 -SiO2 and Li2 O-Al2 O3 -B2 O3 -SiO2. Where the coefficient of thermal expansion is sufficiently low to impart good thermal shock resistance, the compositions can be considered for top-of-stove cooking vessels.
TL;DR: A short review of the methods of preparation of magnetite anodes and the physico-chemical properties of Fe3O4 is followed by experimental results using chlorine evolution as a test reaction.
Abstract: A short review of the methods of preparation of magnetite anodes and the physico-chemical properties of Fe3O4 is followed by experimental results using chlorine evolution as a test reaction. Problems arising in the operation of composite magnetite-titanium structures are considered.
TL;DR: In this article, the authors showed that the hydrothermal decomposition of iron(II) or iron(III) aminopolycarboxylate complexes can produce well-crystallized, stoichiometric Fe3O4.
Abstract: The hydrothermal decomposition of iron(II) or iron(III) aminopolycarboxylate complexes can produce well-crystallized, stoichiometric Fe3O4. Best results were obtained when 0.1 m nitrilotriacetatoiron(III) was decomposed under N2 in 0.2–0.4 m NaOH at 497 K for 70 h or more.
TL;DR: In this article, submicron magnetite (Fe/sub 3/O/sub 4/) powders were sintered in air and in vacuum at 773, 793, and 843/sup 0/K.
Abstract: Submicron magnetite (Fe/sub 3/O/sub 4/) powders were sintered in air and in vacuum at 773, 793, and 843/sup 0/K. Specific surface area measurements were used to monitor the sintering progress. Oxidation of the magnetite altered the sintering kinetics, which were dominated by surface diffusion in this temperature range.
TL;DR: In this paper, a correlation has been found between the oxide intergrowth texture and the temperature and fo2 as calculated using the Buddington & Lindsley geothermometer.
TL;DR: The partial substitution of oxygen by fluorine, in magnetite, has allowed to increase the concentration of the Fe 2+ ions and to modify the ratio (Fe 2+ Fe 3+ ) without introducing a foreign cation.
Journal Article•
TL;DR: Detrital iron-titanium (Fe--Ti) oxide minerals of the ulvospinel-magnetite (titanomagnetite) and ilmenite-hematite (Titanohematite) solid solution series are common in uranium-bearing sandstones.
Abstract: Detrital iron-titanium (Fe--Ti) oxide minerals of the ulvospinel-magnetite (titanomagnetite) and ilmenite-hematite (titanohematite) solid solution series are common in uranium-bearing sandstones. Alteration of Fe--Ti oxide minerals in oxidizing environments formed secondary products (primarily hematite) that are distinct from those produced under reducing conditions (iron disulfide minerals). Oxidation of sulfidized Fe--Ti oxide minerals, by the processes that formed uranium rolls, produced ferric oxide minerals (limonite) having textures that mimic those of the iron disulfides. Titanomagnetite and titanohematite have been severely depleted in the ore-bearing zones of some uranium deposits. The alteration of detrital Fe--Ti oxide minerals near uranium ore deposits may produce characteristic signatures in the magnetization of the sandstone. Knowledge of the distribution and magnetic properties of these minerals can aid in interpreting data from total magnetic-field and magnetic-susceptibility surveys of uranium deposits.
TL;DR: The oxide scale formed on chromium ferritic steels (21/4-9% Cr) by reaction with water/steam in the temperature range 200-570°c consists of an inner Fe/Cr spinel layer and an outer layer of magnetite as mentioned in this paper.
Abstract: The oxide scale formed on chromium ferritic steels (21/4–9% Cr) by reaction with water/steam in the temperature range 200–570°c consists of an inner Fe/Cr spinel layer and an outer layer of magnetite. These layers are often indistinguishablefrom one another when the scale is sectioned and viewed under an optical microscope. Possible etching techniques, able to reveal the two layers (often without affecting the metal surface), have been investigated. Successful techniques are listed and the mechanisms involved are discussed in relation to current knowledge of oxide dissolution and passivation of metal surfaces.
TL;DR: Chelatometric titration of iron after solvent extraction with MIBK from solutions prepared by use of CPA is found to be accurate for samples such as pyrite cinder.
05 Dec 1978-The Journal of the Japanese Association of Mineralogists,Petrologists and Economic Geologists
TL;DR: In this article, the stability and paragenesis of Fe-Ti oxide and silicate minerals in hematite-bearing basic schists are compared to those in hemetite-free ones.
Abstract: The Sanbagawa basic schists in the Shiragayama area, central Shikoku contain hematite, ilmenite, rutile, sphene and some magnetite. Mineral assemblages of Fe-Ti oxide and silicate minerals in hematite-bearing ones are significantly different from those in hematite-free variety. Excluding albite, quartz, epidote, chlorite and phengite, the mineral assemblages of hematite-bearing ones are hematite+riebeckitic actinolite+sphene or hematite+crossite+sphene in the lower grade zone and hematite+ilmenite+rutile+hornblende±magnetite in the higher grade zone. In the other variety, the mineral assemblages are actinolite+sphene±rutile in the lower grade zone, and ilmenite+hornblende in the higher grade zone. Combining the mode of occurrence and chemistry of Fe-Ti oxides and sphene as well as the Mn-Fe2+ partitioning among magnetite, hematite and ilmenite, stability and paragenesis were determined. Magnetite, ilmenite and rutile in the hematite-bearing basic schists occur in the garnet and biotite zones, whereas, in the hematite-free ones, rutile is restricted to the garnet zone at the prograde stage, and ilmenite occurs in the biotite zone. Sphene is widespread in all the zones, but its occurrence is restricted to the lower grade zone at the prograde stage of metamorphism; its occurrence in the higher grade zone postdates major mineralization. The stable oxide mineral assemblages are magnetite+hematite, hematite+rutile, magnetite+hematite+ilmenite, magnetite+hematite+rutile, hematite+ilmenite+rutile and magnetite+hematite+ilmenite+rutile. Ilmenite and hematite contain significant amounts of MnO; the maximum MnO content of ilmenite and hematite are 24.1 and 2.1 wt. per cent, respectively. Therefore, the paragenesis of Fe-Ti oxide minerals can be determined only in the FeO-Fe203-Ti02-MnO system. The stability of Fe-Ti oxide minerals and sphene is controlled by the bulk-rock chemistry as well as pressure, temperature and oxygen fugacity.
Patent•
11 Dec 1978
TL;DR: In this article, a process for recovering magnetite from fly ash is described, where fly ash containing magnetite is made into a slurry having 5% to 10% solids by weight.
Abstract: This invention relates to a process for recovering magnetite from fly ash. Fly ash containing magnetite is made into a slurry having 5% to 10% solids by weight and the slurry is then concentrated in a settling tank to a slurry having approximately 20% solids by weight. The concentrated slurry is delivered to a magnetic separator where the magnetite is separated from the remainder of the fly ash. The magnetite is then crushed in a pulverizer to a size so that 95% of the crushed magnetite will pass through a 325 mesh sieve. The crushed magnetite is then delivered to a second magnetite separator which is weaker than the first magnetic separator to separate the crushed magnetite from any impurities. The purified crushed magnetite is then dried and stored.
TL;DR: In this article, the exsolution process of magnetite in a garnet matrix is described and an ionic process model is proposed for this transitional event, which is in good agreement with the experimental data obtained in electron microscopy.
Abstract: The exsolution process of magnetite in a garnet matrix is described. The intragranular nucleation of magnetite in substituted yttrium iron garnets is characterized by a transitional event. Magnetite nucleates in the centre of zones which constitute a transitional phase fully coherent with the matrix. An ionic process model is proposed for this transitional event. This model is in good agreement with the experimental data obtained in electron microscopy. It is shown that the activation energy barrier is lower for nucleation via a transitional phase.
TL;DR: In this article, the vaporization of magnetite at 1373 to 1673 K was investigated with the help of an omegatron type mass-spectrometer, the method having been modified to carry out quantitative measurements of oxygen partial pressures greatly diminished due to by-pumping taking place in vacuum systems.
TL;DR: In this article, a single-stage separator was used at rates up to 4.4 tons per hour per square foot of matrix cross-section, which is an improvement over drum separators working in the particle size range of the feeds used in this study.
Abstract: A research program at this Laboratory has demonstrated successful recovery of magnetite at high throughput rates from mixtures of magnetite and coal-like those found in a coal-washing circuit-by High Gradient Magnetic Separation (HGMS). Improving the rate of magnetite recovery with HGMS over that found with conventional magnetic separators is an achievement important to the coal cleaning industry. A single-stage separator was used at rates up to 4.4 tons per hour per square foot of matrix cross-section. At this rate more than 99% of the magnetite was trapped along with less than 5% of the coal, an improvement over drum separators working in the particle size range of the feeds used in this study. Data is presented on the effect of loading on magnetite recovery and on non-magnetic material entrainment in the magnetic fraction. This fraction increases with increased loading indicating non-magnetics trapping but the effect is least at the highest material throughput values. Dispersants help to reduce entrainment, also. Some magnetic agglomeration appears to occur as the separation is performed but there seems to be little difference in separator performance on the basis of particle size.
TL;DR: In this paper, the effect of gadolinium on the exsolution mechanism was studied by X-ray microanalysis using a transmission electron microscope; the ionic structure of the garnet lattice indicates that Gd3+ ions allow a shear process which leads to the pretransformed nuclei.
Abstract: Magnetite exsolves from a garnet matrix via a pretransformed nucleus when gadolinium is substituted for yttrium in yttrium iron garnet. The effect of gadolinium on the exsolution mechanism was studied by X-ray microanalysis using a transmission electron microscope; a strong decrease in gadolinium concentration was found within the pretransformed nuclei. The ionic structure of the garnet lattice indicates that Gd3+ ions allow a shear process which leads to the pretransformed nuclei, whereas with Y3+ ion diffusion is the only process for magnetite exsolution.