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Showing papers on "Hematite published in 1969"


Journal ArticleDOI
Robert A. Berner1
TL;DR: In this paper, the differential solubility of hematite and goethite in 0.1 M HCl has been determined at 85°C and it was shown that finely divided limonitic goethites is thermodynamically unstable relative to hematites plus water under practically all geological conditions.

155 citations


Journal ArticleDOI
TL;DR: In this article, it is inferred that under favorable interstitial chemical conditions the iron oxide coatings age to hematite and the clay undergoes postdepositional alteration, yielding additional iron which ultimately forms additional hematitic pigment.
Abstract: Surface weathering on the Sonoran desert produces iron-bearing clay minerals which are concentrated in fine-grained sediments eroded from the desert. The clay fraction of the desert soils and desert-derived alluvium contains an average of about 4.5 percent total iron. An average of less than 1.0 percent iron occurs in oxide coatings on grains; the remainder is held in the clay-mineral lattices. It is inferred that under favorable interstitial chemical conditions the iron oxide coatings age to hematite and the clay undergoes postdepositional alteration, yielding additional iron which ultimately forms additional hematite pigment. Biotite, another important source of iron, commonly is associated with the clay and undergoes similar intrastratal alteration. It is concluded that the characteristic concentration of iron and hematite pigment in mudstones and shales in many ancient red beds, particularly in red beds that are associated with evaporites or aeolian sandstones, or both, reflects initial concentration of iron-bearing clay minerals and biotite in fine-grained sediments derived from desert source areas.

57 citations


Journal ArticleDOI
TL;DR: In this article, powder patterns of magnetic domains on various crystallographic surfaces of pure and doped hematite single crystals have been studied at room temperature and in the vicinity of the Morin transition.
Abstract: Powder patterns of magnetic domains on various crystallographic surfaces of pure and doped hematite single crystals have been studied at room temperature and in the vicinity of the Morin transition. The observations below room temperature were made with an apparatus employing thermoelectric cooling modules. It was concluded that the domains were either slabs or cylinders of irregular transverse cross section with axes lying parallel to the basal plane. The domain walls were determined to be 180° ones. At the Morin transition, a light diffuse colloidal line is formed at the boundary between two phases, one weakly ferromagnetic and the other antiferromagnetic. On warming or cooling, the boundary sweeps across the crystal in a characteristic fashion.

42 citations



Journal ArticleDOI
TL;DR: Granitic batholith petrogenesis study, hypersolidus and subsolidus hydrothermal experiments on calcalkaline igneous rocks, gas phase fractionation tendency of iron, specular hematite in volcanic association, contact metasomatic iron deposits as mentioned in this paper.
Abstract: Granitic batholith petrogenesis study, hypersolidus and subsolidus hydrothermal experiments on calcalkaline igneous rocks, gas phase fractionation tendency of iron, specular hematite in volcanic association, contact metasomatic iron deposits

23 citations


Book ChapterDOI
01 Jan 1969
TL;DR: Goethite is the dominant Fe+3 bearing mineral in all cores from the Red Sea brine deposits with the exception of core station 84 within the Atlantis II Deep where hematite has been transformed from original goethite and limonite.
Abstract: Goethite is the dominant Fe+3 bearing mineral in all cores from the Red Sea brine deposits with the exception of core station 84 within the Atlantis II Deep where hematite has been transformed from original goethite and limonite.

21 citations



Journal ArticleDOI
TL;DR: The solubility of manganese and iron oxides in a melted boraxflux is reported, and the results are used to optimize the conditions for single crystal growth.

9 citations


Book ChapterDOI
01 Jan 1969
TL;DR: In this paper, the magnetic properties of sediment samples recovered from the thermal brine area of the Red Sea have been studied and the minerals which have distinctive magnetic signatures, particularly on heating, are goethite, lepidocrocite, sidersite, manganosiderite, pyrite, hematite and small quantities of a ferrimagnetic mineral, which is probably maghemite.
Abstract: Studies of the magnetic properties of sediment samples recovered from the thermal brine area of the Red Sea have been made. The minerals which have distinctive magnetic signatures, particularly on heating, are goethite, lepidocrocite, siderite, manganosiderite, pyrite, hematite and small quantities of a ferrimagnetic mineral, which is probably maghemite.

9 citations


Journal ArticleDOI
TL;DR: A review of the iron-oxide reduction research at the University of Toronto can be found in this paper, where the authors focus on the kinetics of hydrogen reduction of sintered briquettes made from reagent grade iron oxide with and without small additions of impurities.

7 citations


Patent
19 Mar 1969

Journal ArticleDOI
18 Oct 1969-Nature
TL;DR: In terms of the inverse spinel structure, the maghemite lattice contains 2 cation vacancies per unit cell and the corresponding unit cell content is Fe21.............. III □2 O32, where □ signifies a cation vacancy.
Abstract: FERRIC oxide may exist in either of two stable crystal modifications at room temperature. The α-form, hematite, has a rhombohedral lattice with a0= 5.4228 A and α= 55° 17′, whereas the γ-form, maghemite, has a structure which closely approximates to that of a defective inverse spinel1. In terms of the inverse spinel structure, the maghemite lattice contains 2 cation vacancies per unit cell and the corresponding unit cell content is Fe21 III □2 O32, where □ signifies a cation vacancy.

Journal ArticleDOI
TL;DR: In this article, the rheological behavior of aqueous hematite slurries has been studied by laboratory viscosity and flow measurements, showing that lignosulfonate dispersant additive markedly increased the flow of slurries containing finely divided hematites.
Abstract: The rheological behavior of aqueous hematite slurries has been studied by laboratory viscosity and flow measurements. Data are presented for slurries with volume concentrations of hematite up to 40%. Solids concentration and particle size distribution were found to be important variables in the rheological behavior of hematite slurries as contrasted to temperature which was found to have only a small effect. Chemical dispersant additives and viscosity control additives used in relatively small concentrations improved the flow characteristics of the hematite slurries. Specifically, a lignosulfonate dispersant markedly increased the flow of slurries containing finely divided hematite, −325 mesh, and a viscosity control additive increased the carrying capacity of other slurries for coarse particles.

Patent
07 Jan 1969
TL;DR: In this article, an improved process for the production of metallic iron by direct reduction of iron ores at relatively high temperatures is presented. But the process has special utility with regard to the reduction of specular hematite ores, particularly with carbon monoxide and carbon carbonoxide-containing gases.
Abstract: An improved process for the production of metallic iron by direct reduction of iron ores at relatively high temperatures. The ore is staged in a series of beds, fluidized by contact with ascending gas, and reduced. In ferric reduction zones, ferric oxide (hematite) is reduced to magnetic oxide of iron (magnetite), and the latter is thence reduced to substantially ferrous oxide (wustite). In the ferrous reduction zone, or zones, the ferrous oxide is reduced to metallic iron. By addition or incorporation with the partially reduced ore of a ferrous reduction zone, or zones, of critical amounts of salts formed from Groups I-A, II-A and III-A metals, and metalloids, particularly halide salts and nonoxide-forming hydroxides and carbonates of such metals, the overall rate of reduction of the ore is promoted and metallization increased without significant adverse effects due to bogging. The process has special utility with regard to the reduction of specular hematite ores, particularly with carbon monoxide and carbon monoxide-containing gases.


01 Jan 1969
TL;DR: In this article, the magnetostriction constants of hematite are determined on the basis of these data and the magnetoelastic interaction constants of the substance are evaluated by thermodynamics.
Abstract: The longitudinal and transverse magnetostriction of an hematite single crystal are measured along various crystallographic directions at temperatures between 100 and 300° K in magnetic fields up to 150 kOe. The magnetostriction constants of hematite are determined on the basis of these data and the magnetoelastic interaction constants of the substance are evaluated by thermodynamics. The contribution of magnetoelastic energy to the anisotropy energy of hematite is calculated and it is shown that in the antiferromagnetic region, at temperatures about 20-30° below the Morin temperature, magnetoelastic interaction does not exert a significant effect on the magnetic properties of hematite. By comparing the experimental data with calculations of dipole-dipole energy in hematite it is shown that magnetoelastic interaction in this substance is due to the deformation-dependent dipole-dipole interaction.

Patent
12 Nov 1969
TL;DR: In this paper, the reduced iron is then ground without prior passivation to all pass 100 mesh and with 60 - 80% passing 325 mesh, and the iron may then be sintered in the range 1600' - 2200'F and reground to size.
Abstract: 1,170,690. Reducing iron ore; HYDROCARBON RESEARCH Inc. Sept.19, 1967, No.42703/67. Heading C7D. Iron for powder metallurgical use is obtained by grinding an iron oxide e.g. hematite, magnetite or millscale to all pass a 20 mesh (Tyler) screen with not more than 25% passing 325 mesh, and reducing the ground ore in a fluidized bed at a temperature in the range 600‹ -1100‹ F and a pressure in the range 200-650 p. s. i. with a hydrogen-rich gas; the reduced iron is then ground without prior passivation to all pass 100 mesh and with 60 - 80% passing 325 mesh. The iron may then be sintered in the range 1600‹ - 2200‹F. and reground to size.


Journal ArticleDOI
TL;DR: In this article, the effect of a field up to 120 koe (parallel to the second order axis) on the magnetic structure of a hematite single crystal below the Morin point was investigated.



Journal ArticleDOI
TL;DR: The mineralogy of Nipe clay was characterized by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), and chemical analysts as mentioned in this paper.
Abstract: The mineralogy of Nipe clay was characterized by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), BET surface area, and chemical analysts. The major components of the clay fraction are goethite, gibbsite, hematite and kaolinite. Goethite is the predominant iron oxide as indicated by the high intensity of the XRD peaks. The unit cell dimensions of goethite, estimateod from the XRD data, were a = 4.603 A, b = 9.806 A and c = 3.002 A. The unit cell dimensions of hematite were a = 5.037 A, and c = 13.735 A. The extent of aluminum substitution in goethite and hematite was also estimated from the XRD data. The mole % Al in goethite, based on the d (111) value, was 15.57 mole percent, whereas when the a-dimension of the unit cell was used, a value of 12.86 mole percent was obtained. The estimated mole percent Al substitution in hematite was 0.67. The hematite/goethite ratio as estimated from the relative intensities of the 104 peak of hematite and the 110 peak of goethite was 0.51. Kaolinite showed a high capacity to absorb IR radiation as indicated by strong absorption peaks around 1000 and 3700 cm -1 . The surface area of the clay as determined by the BET method was 55.26 m 2 /g. The ratio of Fe ox /Fe d was very low (1.17x10 -2 ), indicating that the iron oxides occur in well crystallized form.