Grains of magnetite occur in serpentine, as an alteration-product of the olivine.
In emery, magnetite in a granular form is largely associated with the corundum; and in certain kinds of mica magnetite occurs as thin dendritic enclosures.
Closely related to magnetite is the rare volcanic mineral from Vesuvius, called magnoferrite, or magnesioferrite, with the formula MgFe 2 O 4; and with this may be mentioned a mineral from Jakobsberg, in Vermland, Sweden, called jakobsite, containing MnFe204.
Some are black, very thin and curved like threads or hairs (trichites); often a group of these is seated on a small crystal of augite or magnetite and spreads outwards on all sides.
In Englishspeaking countries the ore is commonly known as magnetite, and pieces which exhibit attraction as magnets; the cause to which the attractive property is attributed is called magnetism, a name also applied to the important branch of science which has been evolved from the study of phenomena associated with the magnet.
Many of their compounds are very strongly magnetic, erbium, for example, in Er203 being four times as strong as iron in the familiar magnetite or lodestone, Fe203.
It was at one time proposed to treat the concentrated black iron obtained in the Ural gold washings, which consists chiefly of magnetite, as an iron ore, by smelting it with charcoal for auriferous pigiron, the latter metal possessing the property of dissolving gold in considerable quantity.
The ores are principally magnetites (New York is the largest producer of magnetite ore among the states, producing about 45% of the total for the United States in 1907 and 1908), but red haematites occur in the N.
Of the city are the Cornwall (magnetite) iron mines, from which about 18,000,000 tons of iron ore were taken between 1740 and 1902, and 804,848 tons in 1906.
P roductive magnetite deposits in the world.
The brownish colour of some slates is due to limonite and haematite, but magnetite occurs in the darker coloured varieties.
On ignition the reaction, 8A1+3Fe 3 O 4 =9Fe+4Al 2 O 3, gives a temperature estimated to be between 2,300° and 2,700°C. The reaction, stated in weights, means that 217 parts of aluminium plus 732 parts magnetite (iron oxide) equals 540 parts steel plus 409 parts slag, or approximately 3 parts of aluminium plus 10 parts of magnetite will produce, on combustion, 7 parts of steel.
But the state's iron foundries moved rapidly westward after the first successful experiments in making pig-iron with bituminous coal, in 1845, and the discovery, a few years later, that rich ore could be obtained there at less cost from the Lake Superior region resulted in a decline of iron-mining within the state until, in 1902, the product amounted to only 822,932 long tons, 72.2% of which was magnetite ore from the Cornwall mines in Lebanon county which have been among the largest producers of this kind of ore since the erection of the Cornwall furnace in 1742.
In 1908 the entire iron-ore product of the state, amounting to 443,161 long tons, was not 1.3% of that of the United States, but the production of the magnetite-ore alone (343,998 long tons) was more than onefifth that of all the United States.
It is never crystallized, but may have a fibrous or microcrystalline structure, and commonly occurs in concretionary forms or in compact and earthy masses; sometimes mammillated, botryoidal, reniform or stalactitic. The colour presents various shades of brown and yellow, and the streak is always brownish, a character which distinguishes it from haematite with a red, or from magnetite with a black streak.
In many cases it has been formed from other iron oxides, like haematite and magnetite, or by the alteration of pyrites or chalybite.
They are four important iron ores, magnetite, haematite, limonite and siderite, and one of less but still considerable importance, pyrite or pyrites.
Magnetite, Fe 3 0 4, contains 72.41% of iron.
In some cases the iron-bearing mineral, such as magnetite or haematite, can be separated from the gangue after crushing, either mechanically or magnetically, so that the part thus enriched or " concentrated " alone need be smelted.
- The Archaean crystalline rocks abound in deposits of magnetite and red haematite, many of them very large and rich.
The middle states, New York, New Jersey and Pennsylvania, are known to have many great deposits of rich magnetite, which supplied a very large proportion of the American ores till the discovery of the very cheaply mined ores of Lake Superior.
The magnetite ore bodies which supply this industry lie in a band about 180 m.
In Swedish Lapland, near the Arctic circle, are the great Gellivara, Kirunavara and Luossavara magnetite beds, among the largest in Europe.
Under all these three conditions the diamond is associated with fragments of the rocks of the country and the minerals derived from them, 'especially quartz, hornstone, jasper, the polymorphous oxide of titanium (rutile, anatase and brookite), oxides and hydrates of iron (magnetite, ilmenite, haematite, limonite), oxide of tin, iron pyrites, tourmaline, garnet, xenotime, monazite, kyanite, diaspore, sphene, topaz, and several phosphates, and also gold.
The other minerals found in the concentrates are pebbles and fragments of pyrope, zircon, cyanite, chrome-diopside, enstatite, a green pyroxene, mica, ilmenite, magnetite, chromite, hornblende, olivine, barytes, calcite and pyrites.
This was burnt mouth-down in the oven., and the ashes on the ground reduced the red haematite to black magnetic oxide of iron; some traces of carbonyl in the ash helped to rearrange the magnetite as a brilliant mirror-like surface of intense black.
There are extensive deposits of iron ore (magnetite and hematite) in the province of Bulacan, Luzon.
It thus resembles magnetite in external characters, but is readily distinguished from this by the fact that it is only slightly magnetic. It is found in considerable amount, associated with zinc minerals (zincite and willemite) in crystalline limestone, at Franklin Furnace, New Jersey, where it is mined as an ore of zinc (containing 5 to 20% of the metal); after the extraction of the zinc, the residue is used in the manufacture of spiegeleisen (the mineral containing 15 to 20% of manganese oxides).
The formation is very uniform in its character, the gneiss having a red colour and containing small granules of magnetite, but, nevertheless, not a single iron mine belongs to this region.
Nearly all the ore is magnetite, and in the midlands it is almost wholly free of phosphorus.
The product of the iron mines has fluctuated greatly in quantity, being nearly 1,000,000 tons of ore in 1892, 257,235 tons in 1897, and 549,760 tons in 1907, when the output was valued at $1,815,586, and was about nine-tenths magnetite and one-tenth brown ore.
Iron is widely diffused, principally in the form of magnetite, brown haematite, limonite and bog iron.
The beds of magnetite and hematite, in the southern portion of the Wasatch Mountains, are the largest in the western United States; in 1902 the four productive mines in Milford, Juab and Utah counties produced 16,240 tons of ore, valued at $27,417.
4.1 Chemical Reactivity 4.2 Solubility 4.3 Compounds 4.4 Ferrous Oxide 4.5 Magnetite 4.6 Ferric Acid 4.7 Halogen Compounds 4.8 Ferric Chloride 4.9 Ferrous Bromide 4.10 Sulfur(Sulphur)Compounds 4.11 Nitrides and Nitrates 4.12 Phosphides, Phosphates 4.13 Arsenides and Arsenites 4.14 Carbides, Carbonates 4.15 Medical Uses
Magnetite, Fe304, may be regarded as ferrous ferrite, FeO-Fe2O3.
Iron, on the contrary, especially magnetite, is found abundantly and has for long been worked by the Malagasy with the simple appliances brought by their ancestors from their original home in the Far East.
Magnetite, or magnetic iron, the richest of all iron ores, is found in abundance near Wallerawang in New South Wales.
Magnetite occurs in great abundance in Western Australia, together with haematite, which would be of enormous value if cheap labour were available.
Considerable quantities of the following minerals have been found: barytes (heavy spar), magnetite (magnetic iron ore), and pyrolusite (manganese dioxide) in Humboldt county; roofing slate in Esmeralda county; cinnabar (ore containing quicksilver) in Washoe county; haematite in Elko and Churchill counties; cerussite and galena (lead ores) in Eureka county; and wolframite (a source of tungsten) at Round Mountain, White Pine county.
In 1908 the product amounted to 48,522 long tons (all magnetite), and was valued at $76,877; almost the entire product is from the Cranberry mines, near Cranberry, Mitchell county.
Magnetite is a mineral of wide distribution, occurring as grains in many massive and volcanic rocks, like granite, diorite and dolerite.
Large ore-bodies of granular and compact magnetite occur as beds and lenticular masses in Archean gneiss and crystalline schists, in various parts of Norway, Sweden, Finland and the Urals; as also in the states of New York, New Jersey, Pennsylvania and Michigan, as well as in Canada.
Liversidge has shown that magnetite is probably present.
By deoxidation, haematite may be converted into magnetite, as proved by certain pseudomorphs; but on the other hand magnetite is sometimes altered to haematite.
Magnetite production was confined to mountain regions in the east and west, and only in Ohio were carbonates mined.
Among the commonest associates of the diamond are quartz, topaz, tourmaline, rutile, zircon, magnetite, garnet, spinel and other minerals which are common accessory constituents of granite, gneiss and the crystalline schists.