Chemical elements
  Iron
    History of Iron
    Mineralogy
      Native Iron
      Magnetites
      Haematites
      Carbonates
      Sulphides
      Iron Minerals
      Sources of Iron
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
    Corrosion
    Iron Salts
    PDB 101m-1aeb
    PDB 1aed-1awd
    PDB 1awp-1beq
    PDB 1bes-1c53
    PDB 1c6o-1ci6
    PDB 1cie-1cry
    PDB 1csu-1dfx
    PDB 1dgb-1dry
    PDB 1ds1-1e08
    PDB 1e0z-1ehj
    PDB 1ehk-1f5o
    PDB 1f5p-1fnp
    PDB 1fnq-1fzi
    PDB 1g08-1gnl
    PDB 1gnt-1h43
    PDB 1h44-1hdb
    PDB 1hds-1i5u
    PDB 1i6d-1iwh
    PDB 1iwi-1jgx
    PDB 1jgy-1k2o
    PDB 1k2r-1kw6
    PDB 1kw8-1lj0
    PDB 1lj1-1m2m
    PDB 1m34-1mko
    PDB 1mkq-1mun
    PDB 1muy-1n9x
    PDB 1naz-1nx4
    PDB 1nx7-1ofe
    PDB 1off-1p3t
    PDB 1p3u-1pmb
    PDB 1po3-1qmq
    PDB 1qn0-1ra0
    PDB 1ra5-1rxg
    PDB 1ry5-1smi
    PDB 1smj-1t71
    PDB 1t85-1u8v
    PDB 1u9m-1uyu
    PDB 1uzr-1vxf
    PDB 1vxg-1wri
    PDB 1wtf-1xlq
    PDB 1xm8-1y4r
    PDB 1y4t-1ygd
    PDB 1yge-1z01
    PDB 1z02-2a9e
    PDB 2aa1-2azq
    PDB 2b0z-2boz
    PDB 2bpb-2ca3
    PDB 2ca4-2cz7
    PDB 2czs-2dyr
    PDB 2dys-2ewk
    PDB 2ewu-2fwl
    PDB 2fwt-2gl3
    PDB 2gln-2hhb
    PDB 2hhd-2ibn
    PDB 2ibz-2jb8
    PDB 2jbl-2mgh
    PDB 2mgi-2o01
    PDB 2o08-2ozy
    PDB 2p0b-2q0i
    PDB 2q0j-2r1h
    PDB 2r1k-2spm
    PDB 2spn-2vbd
    PDB 2vbp-2vzb
    PDB 2vzm-2wiv
    PDB 2wiy-2xj5
    PDB 2xj6-2ylj
    PDB 2yrs-2zon
    PDB 2zoo-3a17
    PDB 3a18-3aes
    PDB 3aet-3bnd
    PDB 3bne-3cir
    PDB 3ciu-3dax
    PDB 3dbg-3e1p
    PDB 3e1q-3eh4
    PDB 3eh5-3fll
    PDB 3fm1-3gas
    PDB 3gb4-3h57
    PDB 3h58-3hrw
    PDB 3hsn-3ir6
    PDB 3ir7-3k9y
    PDB 3k9z-3l4p
    PDB 3l61-3lxi
    PDB 3lyq-3mm8
    PDB 3mm9-3n62
    PDB 3n63-3nlo
    PDB 3nlp-3o0f
    PDB 3o0r-3p6o
    PDB 3p6p-3prq
    PDB 3prr-3sel
    PDB 3sik-3una
    PDB 3unc-4blc
    PDB 4cat-4erg
    PDB 4erm-4nse
    PDB 4pah-8cat
    PDB 8cpp-9nse

Magnetites





Magnetite or Lodestone

Magnetite or Lodestone, Fe3O4 or Fe2O3.FeO, is the richest form of iron ore, containing when pure 72.4 per cent, of metal. Magnetite crystals are usually octahedra and dodecahedra, and are well developed in some chlorite schists. Good crystals have been found at Nornmark in Wermland. They are not scratched by a knife, their hardness on Mohs' scale ranging frem 5.5 to 6.5, and their density from 4.9 to 5.2. Magnetites in the massive form are widely distributed, occurring in large quantities in India, Sweden, South Africa, Russia, Siberia, Canada, and the United States. The Indian deposits are located in the Madras Presidency, and are estimated at milliards of tons, but, owing to the scarcity of fuel, they have not been worked on a large scale. Of even greater magnitude are the American deposits in the neighbourhood of Lake Superior, which form the largest source of iron ore in the world. The metal in these ores ranges from 55 to 65 per cent.

Some of the Swedish magnetites are very pure, and are used in the manufacture of Swedish iron, which is noted for its high quality. As the name implies, magnetite possesses magnetic properties, sometimes exhibiting polarity. Specimens possessing the most powerful magnetism are found in Siberia and the Harz Mountains. It is on account of this property that the ores can be concentrated magnetically on a commercial scale. The colour varies from brownish grey to iron black. When compact, the mineral is opaque, but translucent dendrites have been found in mica, exceedingly thin, and ranging in colour from almost colourless to pale smoky brown. The mineral has a subconchoidal fracture which is bright when fresh. It is fusible only with difficulty; soluble in hydrochloric acid.

According to Nicander, the name magnetite is derived from Magnes, the shepherd, who discovered it in consequence of his shoe-nails being drawn from their soles as he drove his flocks to pasture. More probably the name is derived from Magnesia, a town in Asia Minor, where magnetite was discovered.


Chrome iron ore

A pseudomorph of magnetite has been described under the name of dimagnetite, which crystallises in elongated prisms, black in colour and possessed of feeble lustre. It occurs implanted on crystals of magnetite, is magnetic, and probably has an analogous composition to magnetite. Several varieties of magnetite are known in which the ferrous or ferric, or even both, irons are more or less replaced by other metals. The more important of these are: -

Chromite, chromo-ferrite, sidero-chrome, or chrome iron ore, FeO.Cr2O3, in which the ferric oxide of magnetite is replaced by chromium sesqui-oxide. This ore constitutes the main source of chromium compounds, and, on account of its infusibility, is sometimes utilised in furnaces for linings. Chromite is widely distributed, being found in Sweden, Germany, Northern Caucasus, India, Canada, the United States, Rhodesia, New Caledonia, Turkey and Greece. Rhodesia yields more chrome iron ore than any other country, the production in 1912 amounting to 61,857 tons. Chromite occurs in small quantities in most meteorites. The ore resembles magnetite in appearance, having a black colour and a similar crystalline form. It sometimes exhibits magnetic properties; hardness 5.5; density 4.3 to 4.6. It leaves a brown streak.

Acids do not attack chromite, but fusion with alkali hydrogen sulphates effects its decomposition. The Grecian ore, which occurs mainly in the Eastern Provinces and in the island of Skyros, is particularly refractory on account of the impurities it contains. Chrome iron ores containing some Fe2O3 may be regarded as mixtures of chromite and chromitite Platiniferous chromites are found in the Urals.

Franklinite

Franklinite, (Mn, Zn)O.Fe2O3, is a magnetite in which the ferrous oxide is more or less replaced by zinc oxide and manganous oxide, which latter imparts a red colour to the ore. It is found in New Jersey, U.S.A., in large black octahedra, and in recognition of its zinc content is frequently called zincite. It is slightly magnetic. Hardness 5.5 to 6.5. Density 5.07 to 5.2. It is infusible in the blowpipe; soluble in concentrated hydrochloric acid.

Titanic iron ore

Ilmenite, titanic iron ore or ferrous titanite, FeO.TiO2, is the ore in which titanium was first discovered. It takes its name from the Ilmen Mountains. In the massive form it occurs in Norway, whilst in Canada, the United States, India, and New Zealand, it is met with as sand. Well-formed crystals are rare, but differ from those of the preceding minerals in that they belong to the hexagonal system, and not to the cubic. They have almost the same angles (viz. 94° 29') as those of haematite (viz. 94° 0') (vide infra).

Ilmenite is faintly but decidedly magnetic; hardness 5.5; density 4.8. It usually contains from 26 to 30 per cent, of titanium, although specimens have been found containing considerably more and considerably less than this amount. The density falls with increase of titanium, and the axial ratio a: с likewise falls, indicating an increase in the vertical axis, с. This is well illustrated by the following data: -

TiO2. Per cent.Density.Axial Ratio, a: c.
5.665.0411: 1.368
21.584.9101: 1.3716
47.684.8521: 1.3772
49.684.6141: 1.379
57.23...1: 1.3851


The formula for ilmenite may also be written as Fe2O3.Ti2O3, and, on account of the difficulty of determining the state of oxidation of the titanium, it is not easy to decide, from chemical considerations alone, which formula is correct, although the balance of chemical evidence appears to support the formula FeO.TiO2. The mineral crystallises, however, in the rhombohedral-tetartohedral division of the hexagonal system, and the axial ratio in no case lies between that of haematite, Fe2O3,

a: c = 1: 1.359, and that of artificial titanium sesqui-oxide, Ti2O3, namely
a: c = 1: 1.316,

as it might be expected to do if it were an isomorphous mixture of Fe2O3.Ti2O3. This lends strong support to the view that the mineral is a titanite of ferrous iron, namely FeTiO3.

Other varieties of this mineral are known as kibdelophane and crichtonite, containing about 30 per cent, of titanium; menaccanite, hystastite, and uddevallite, containing some 25, 15 to 20, and 10 per cent, of titanium respectively.

In Geikielite, from Ceylon, part of the iron is replaced by magnesium, thus (Mg, Fe)O.TiO2. Density 3.976. Axial ratio,

a: c = 1: 1.370.

It is isomorphous with senaite, (Fe, Mn, Pb)O.TiO2, which is likewise hexagonal, having axial ratios

a: c = 1: 0.997.

The crystals are black, thin crystals showing a greenish colour by transmitted light.

Bixbyite

Bixbyite, FeO.MnO2, occurs as brilliant black, cubic crystals, possessed of metallic lustre. The composition of bixbyite might also be written as Fe2O3.Mn2O3. If such were correct, however, the mineral might be expected to crystallise in the hexagonal system, and belong to the haematite group.

Magnesio-ferrite

Magnesio-ferrite or magno-ferrite, MgO.Fe2O3, is a variety of magnetite in which the ferrous oxide has been replaced by magnesia. It crystallises in regular octahedra, and resembles magnetite in colour and general appearance. It is magnetic; hardness 6 to 6.5; density 4.57 to 4.65. It has been found around the fumaroles of Vesuvius. Hydrochloric acid attacks it only with difficulty.

In Ludwigite part of the magnesium oxide is replaced by ferrous oxide, and boric oxide is associated with the ferric oxide. Thus (Mg, Fe)O.Fe2O3.B2O3, or perhaps 3MgO.B2O3 + FeO.Fe2O3.
© Copyright 2008-2012 by atomistry.com