DIAMOND: ORIGIN 235 



A few authorities, including the mineralogist, J. N. Fuchs, suppose that large amounts 

 or carbon dioxide are present in many places in the interior of the earth, and that this has 

 played an essential part in the formation of the diamond. 



Gohel suggested that at high temperatures carbon dioxide might be reduced by certain 

 metals, such as aluminium, magnesium, calcium, iron, or by silicon, &c., the carbon 

 ci'ystallising out during the reduction as diamond. In connection with the existence of 

 drops of liquid carbon dioxide enclosed in cavities in certain diamonds, Simmler stated the 

 opmion that liquid carbon dioxide at a high temperature and pressure is capable of dissolving 

 carbon, and that from this solution carbon may crystallise out as diamond. These 

 assumptions were not, however, supported by the investigations of Gore and of Dolter, 

 who failed to establish the solubility of carbon either in liquid carbon dioxide or in 

 gaseous carbon dioxide above the critical temperature and under great pressure. 



The compounds of carbon with chlorine are sometimes assumed to be the original soui'ce 

 of the carbon of the diamond. A. Favre, and later H. St. Claire Deville, admitted the 

 possibility of the formation of diamond from such compounds, the former having been 

 induced to entertain this idea from the fact that certain minerals associated with the diamond 

 in Brazil can be artificially produced from chlorine compounds. Gorceix, who was well 

 acquainted with Brazilian dej)osits, considered such an origin for diamonds from this region 

 to be quite within the range of possibility, the carbon being supplied by chlorine or fluorine 

 compounds. Without committing himself to any details of the process, Damour also 

 considers it possible that Brazilian diamonds may have originated by the interaction of a 

 variety of suitable conipounds. Finally, we may mention the hypothesis for which Gannal is 

 responsible, namely, that the diamond may have been formed by the decomposition of carbon 

 bisulphide. Other possible modes of formation will be mentioned when the methods 

 employeil in the artificial production of diamonds are under consideration. 



A consideration of the character of the various diamantiferous deposits, which are 

 scattered over the face of the globe, and often widely separated, leads inevitably to the 

 conclusion that there is no single mode of origin common to all diamonds, but that in 

 different deposits the diamond has originated in different ways. Ifthe diamond really occurs 

 in India and Lapland embedded as an original constituent in granite-veins penetrating 

 gneiss, and in South Africa in an olivine-rock associated with gneiss, it almost certainly 

 follows that in these localities the diamond has been formed in the same way as the igneous 

 rock in which it occurs. 



Unfortunately, however, this brings us no nearer the truth, for the exact mode of 

 formation of such rocks is still one of the obscure questions of geology. It is probable that 

 such granite-veins (pegmatite) are due to the solidification, presumably at not very high 

 temperatures, of masses of fused silicates saturated with water. Such a mode of origin is, 

 however, not likely in the case of the gneisses and rocks interfoliated with them, such as the 

 olivine-rock in which the diamonds of the Cape were originally contained, and in the 

 alteration product of which, namely, the serpentine-breccia, they are now found. If, on the 

 other hand, this original olivine-rock is not interfoliated with gneiss at some depth below 

 the earth's surface, but is an eruptive rock which has penetrated the gneiss, as Carvill 

 Lewis has urged, then its mode of origin may not differ essentially from that of pegmatite, 

 and the South African diamonds may have been formed in the same way as those of India 

 and Lapland. If, then, in these countries the diamond is, or has been, a constituent of an 

 icrneous rock, we must conclude that it was during the cooling and solidifying of the fused 

 mass of rock that the diamond crystallised out, the carbon of its substance, if not present 

 as a normal constituent of the x-ock, being derived from bituminous foreign matter. The 



