Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/301

 IKON 285 II. NATURAL SOURCES OF IRON. 4. Meteoric Iron. Metallic iron in a more or less pure condition is occasionally met with in nature, but the supply of metal from this source is wholly inconsiderable. Pro bably nearly all such substances are of meteoric origin, with the exception of ferruginous metallic platinum. Cer tain masses of oxidized iron with unoxidized metal in the interior have been found in Saxony and elsewhere; but great doubt exists as to whether these substances are not artificially prepared metal which has rusted exteriorly in the course of time. Near Nery (France), at a spot where a seam of coal had been burning for some time, Mossier found a mass of a very hard steely iron weighing upwards of 1 (5 ft), together with smaller lumps, evidently formed by the reducing action of the burning coal on ferruginous matter in the soil and rock. True meteoric iron usually if not invariably contains nickel to the extent of from 1 or 2 parts per 100 of iron (as in meteorites analysed by Prout) up to considerably larger amounts. The following analyses of various specimens of meteoric iron consisting wholly or almost entirely of unoxidized substances may be taken as representing the general composition of the substance : Source -I Zacatecas, Mexico. Lenarto. Krasnoyarsk, Siberia (Pallas Meteorite). Bohnini- litz, Bohemia. Cosbv s Creek, Tennessee. Cape of Good Hope. Analyst H. Muller. Wchrle. Berzelius. Berzelius. Bergemann Cnccechea Specific gra-; vity !j 7-78 to 7-84 7-14 to 7-71 7-26 6-G3 to 7-94 90-91 5 -65 0-42 trace trace 0-23 90-883 8-450 0-665 6-002 88-27 10-82 0-46 0-13 0-07 0-10 0-11 0-04 trace 95-25 4-15 0-21 o oi 6 : 32
 * 03

91-89 6-70 0-33 6-09 0-13 81 20 1509 256 009 6 -95 Nickel Cobalt Manganese. Copper Magnesium Phosphorus Carbon Sulphur Tin 0-07 j Silica, &amp;lt;tc. ... 3-22 100-50 100-000 100-00 10000 99-19 99-89 Many meteorites consist of nickeliferous iron intermixed with larger or smaller amounts of oxidized minerals, in particular olivine, augite, labradorite, and other silicates, together with chrome iron stone, magnetic pyrites, magnetic oxide of iron, and schreibersite (phosphide of nickel and iron), &c. On solution in acids many of these substances are left undissolved, especially schreibersite ; in consequence meteorites of mainly metallic character often exhibit peculiar crystal line figures (something like the &quot;moiree metallique&quot; produced by pouring acids on tinplate) when etched by acids (WiedmanstJidt s figures). Nordenskjold has recently shown that many meteorites that have fallen at different times exhibit great uniformity in composition, so that it is highly probable that they all had a common extra-terrestrial origin. Graham found (Proceed ings of Royal Society, xv. 502, 1867) that the Lenarto iron yielded on heating in vacuo 2 85 times its volume of gas, containing Hydrogen 85 68 per cent. Carbon oxide 4 46 ,, ,, Nitrogen 9 86 ,, ,, whilst ordinary malleable iron (horse-shoe nails) yielded a rather smaller amount of gas, of which carbon oxide and dioxide consti tuted the majority; from the fact that he wasunabhB to impregnate ordinary metallic malleable iron with more than about its own vol ume of hydrogen, whilst this meteoric metal contained upwards of two and a half times its volume of that gas, Graham concluded that the meteorite was derived from a cosmical body possessing a dense atmosphere of hydrogen, such as spectrum analysis indicates as ex isting in various fixed stars, of which a Lyrse may be taken as a type. 5. Ores of Iron. Cutting instruments of a rough charac ter have been fashioned by savage and semi-savage nations from meteoric iron ; but the sources from which the metal is practically extracted are those ores in which the metallic properties of the element are masked by its combination with non-metallic substances. These ores are essentially divisible into three classes, viz., those respectively in which the iron exists as sulphide, as carbonate, and as oxide. The first class of ore is best exemplified by pyrites or iron disulphide, FeS 2 ; comparatively little iron is directly pro duced from ores of this class, although the impure ferric oxide obtained from the residue left in the vitriol works after combustion of pyrites and extraction of copper from the residue, known as &quot;purple ore&quot; or &quot;blue billy,&quot; is utilized as &quot; fettling &quot; in the puddling operation, and has sometimes been employed on the spot where it is produced as a source of finely divided metallic iron for the precipita tion of the more valuable copper, the reduction being simply effected by heating together the iron oxide and small coal, or by passing over the heated oxide reducing gases prepared by the partial combustion of coal or other fuel, &c. It maybe noticed in passing that theferrum redactum of pharmacy, or spongy metallic iron, is produced in much the same way, purer materials being employed, ordinarily a pure ferric oxide or hydrated ferric oxide and hydrogen gas; and that several methods for the reduction of iron on a manufacturing scale from various ores based on the same principle have been attempted hitherto without much commercial success ( 30). The ores in which iron exists as carbonate, FeCO 3, are essentially of two kinds, viz., those in which the ferrous carbonate is crystalline and but little admixed with earthy matters, and those in which a larger or smaller amount of clayey matter is intimately intermixed with the ferruginous com pound : the former class is generally termed spathic iron ore (sparry ore, siderite, spathose), and often contains a notable amount of magnesium or of manganese carbonate; the latter class is from its texture and appearance generally spoken of as day ironstone or argillaceous iron ore. Large deposits of a variety of clay ironstone exist in the Coal Measures, frequently alternating with layers of carbonaceous matter, whence the term blackband is applied to this variety. In many cases deposits of spathose and of clay ironstone have become more or less altered by the action of air and moisture, the effect of which is to convert ferrous carbonate into ferric oxide ; in other instances by the action of heat derived from the underlying strata by conduction, or due to trap dykes and analogous volcanic agency, the ferrous carbonate is more or less completely converted into an iron oxide akin to magnetic oxide, so that the deposits of spathose ore or clay ironstone shade off in places into deposits of the iron oxide class. The third class of iron ores in which the iron exists as oxide may be divided into three subclasses, viz., those in which the iron respectively exists as anhydrous ferric oxide, Fe 2 O.j, as hydrated ferric oxide, Fe 2 3 ,H 3 O, or other hydrate, and as ferrous and ferric oxides combined, of which magnetic oxide of iron Fe 3 O 4 is the type. To the first division belong the red haematite and specular ores, to the second brown haematite and bog iron ore, and to the third the magnetic iron ore properly so called, or loadstone, and various modifications of this found in different locali ties, and usually also designated as magnetic ore, although frequently not possessed of strongly marked magnetic pro perties, and also the ironsands of India, New Zealand, St Lawrence, and elsewhere. These latter are usually almost pure Fe 3 4, intermixed with more or less silicious matter (often titaniferous), and are distinguished by their remark able freedom from tendency to take up oxygen and pass into the state of ferric oxide, the which property is not by any means possessed to an equal extent by all so-called magnetic ores ; just as deposits of ferrous carbonate by the action of heat, air, and moisture become changed, so beds of ore exhibiting in the main a composition akin to that of magnetic oxide of iron often contain portions which have become converted by similar agencies into ores more re sembling red or brown haematite. Owing also to the variable intermixture of gangue of various kinds with the veins of iron ore, the physical properties of the substances become more or less altered, so that it is often difficult to