SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



existence of enclosures of liquid cai-bon dioxide in the minerals of such rocks, especially in 

 the quartz of gratlite and gneiss, but also in olivine and even in diamond itself, has a special 

 significance in this coimection. Luzi has demonstrated that in the presence of water and 

 of compounds of fluorine, carbon is soluble in a fused silicate. Though in the experiments 

 of this investigator the dissolved carbon separated out in the form not of diamond but of 

 graphite, it is not inconceivable that under other conditions, such as the high pressure and 

 temperature of the earth's interior and the presence of other substances, diamond itself 

 might be formed. The more recent experiments of I. Friedlander (1898) have demonstrated 

 that graphite is soluble in fused olivine, and that on cooling diamond separates out, facts 

 which have an important bearing on the origin of South African diamonds. 



The diamonds which, together with crystals of quartz and other minerals, are found 

 in crevices in the itacolumite of Brazil must have originated in quite a different way. 

 There is not the slightest doubt that the crystals of quartz and of the accompanying 

 minerals have been deposited from aqueous solution, perhaps even at ordinary temperatures. 

 If this mode of occurrence of the diamond is really a fact, we can only assume that the 

 diamond originated in the same way as the minerals with which it is associated, but as to 

 the nature of a solution capable of depositing diamonds only negative statements can 

 be made. Gorceix, who first expressed the opinion that Brazilian diamonds originated in 

 the same way as the minerals with which they are associated, considered that this common 

 origin must be sought not in the direction of deposition by solution, but rather in the 

 interaction of gases, such as compounds of chlorine and fluorine and water-vapour rising up 

 from the interior of the earth. 



The diamonds of the Adolphskoi gold-washings in the Urals have been supposed to 

 have been originally embedded in a bituminous dolomite. Engelhardt, who first suggested 

 the probable identity of the bituminous dolomite with the mother-rock of the diamonds of 

 this district, supposed the diamonds to have originated by the transformation of the 

 bituminous material, but made no suggestion as to the means whereby such a transformation 

 might be effected. 



The occurrence of diamond in the meteoric stone of Novo-Urei, on account of its 

 association with olivine and augite, is comparable with its occurrence in South Africa, and 

 the mode of origin of the diamond in South Africa and in extra-terrestrial matter of this 

 type is probably one and the same. The origin of diamond in meteoric iron is, however, 

 of a diffl;rent kind. Under ordinary conditions the excess of carbon taken up by molten 

 iron crystallises out on cooling in the form of graphite, and crystals of this modification of 

 carbon are frequently to be seen both in ordinary cast-iron and in most meteoric irons. 

 Moissan, however, has recently demonstrated that when a mass of molten iron solidifies under 

 great pressure, the carbon separates out as diamond. The existence of diamond in meteoric 

 iron may conceivably be due to causes other than high pressure during its solidification, 

 such, for example, as the presence of nickel, phosphorus, and other chemical elements. 



It is obvious from what has been said that the origin of the diamond in nature .is still 

 to a great extent shrouded in mystery. For the complete elucidation of the problem 

 further study of the various modes of occurrence of the precious stone, and of the 

 minerals associated with it, together with more extended experiments in its artificial 

 production, are desirable and necessary. 



Very few facts shedding light on the problem as to the origin of diamond have hitherto 

 been gleaned from experiments in the artificial production of the precious stone, the 

 observation and study of diamantiferous deposits having been a much more fruitful method 

 of attacking the problem. Although various experimenters have from time to time asserted 



