IRON, COBALT AND NICKEL 319 



the doctrine concerning meteorites, and therefore the fact of their 

 containing rocky (siliceous) matter and metallic iron shows that outside 

 the earth the elements and their aggpegation are in some degree the 

 same as upon the earth itself. 



The most widely diffused terrestrial compound of iron is iron 

 bisulphide, FeS 2 , or iron pyrites. It occurs in formations of both 

 aqueous and igneous origin, and sometimes in enormous masses. It is 

 a substance having a greyish-yellow colour, with a metallic lustre, and a 

 specific gravity of 5*0 ; it crystallises in the regular) system. 2 bis 



The oxides are the principal ores used for producing metallic iron. 

 The majority of the ores contain ferric oxide, Fe. 2 O 3 , either in a 

 free state or combined with water, or else in combination with ferrous 

 oxide, JTeO The species and varieties of iron ores are numerous and 

 diverse. Ferric oxide in a separate form appears sometimes as crystals 

 of the rhombohedric system, having a metallic lustre and greyish steel 

 colour ; they areJbrittle, and form a red powder, specific gravity about 

 5-25. Ferric oxide in type of oxidation and properties resembles 

 alumina ; it is, however, although with difficulty, soluble in acids even 

 when anhydrous. The crystalline oxide bears the name of specular 

 iron ore, but ferric oxide most often occurs in a non-crystalline form, 

 in masses having a red fracture, and is then known as red hcematite. 

 In this form, however, it is rather a rare ore, and is principally found 

 in veins. The hydrates of ferric oxide, ferric hydroxides, 3 are most. 



of aerolites), it is readily understood why they should be composed of metallic 

 iron, and this would explain its occurrence in the depths of the earth, which we 

 assumed as the basis of our theory of the formation of naphtha (Chapter VIII., Notes 

 67-60). 



* bls Immense deposits of iron pyrites are known in various parts of Russia. On the 

 river Msta, near Borovitsi, thousands of tons are yearly collected from the detritus of 

 the neighbouring rocks. In the Governments of Tou!a, Riazan, and in the Donets district 

 continuous layers of pyrites occur among the coal seam". Very thick beds of pyrites 

 are also known in many parts of the Caucasus. But the deposits of the Urals are par 

 ticularly vast, and have been worked for a long time. Amongst these I will only indicate 

 the deposits on the Soymensky estate near the Kishteimsky works; the Kaletinsky 

 deposits near the Virhny-Isetsky works (containing 1-2 p.c. Cu) ; on the banks of the 

 river Koushaivi near Koushvi (3-5 p.c. Cu), and the deposits near the Bogoslovsky 

 works (3-5 p.c. Cu). Iron pyrites (especially that containing copper which is extracted 

 ifter roasting) is now chiefly employed for roasting, as a source of SO^ for the manufac* 

 ture of chamber sulphuric acid (Vol.1, p. 291), but the remaining oxide of iron is per- 

 fectly suitable for smelting into pig iron, although it gives a sulphurous pig iron (the 

 sulphur may be easily removed by subsequent treatment, especially with the aid of 

 ferro-manganese in Bessemer's process). The great technical importance of iron pyrites 

 leads to its sometimes being imported from great distances; for instance, into England 

 from Spain. Besides which, when heated in closed retorts FeS^ gives sulphur, and if 

 allowed to oxidise in damp air, green vitriol, FeSO 4 . 



3 The hydrated ferric oxide is found in nature in a dual form. It is somewhat rarely 

 met with in the form of a crystalline mineral called gttthite, whose specific gravity is i'4 



*c 



