THE GENESIS OF THE DIAMOND. 203 



inite diamond crystals and graphite have been found in the meteor- 

 ites from Canon Diablo, Arizona. 



Professor Lewis advanced the theory that probably the diamonds 

 came from the hydrocarbon Avhich was contained in the fragments of 

 carbonaceous shales distributed through the blue ground, but the in- 

 clusion of carbonaceous shales in the blue ground can hardly be rec- 

 onciled Avith Professor Lewis's conclusion " that the rock was a true 

 lava." 



If the diamond is the result of the intrusion of igneous rocks into 

 and through the carbonaceous shales, why do not all pipes composed 

 of kimberlite contain diamonds? And why do diamonds exist in 

 some mines, such as those in the Pretoria district, where no carbona- 

 ceous shales are to be found ? 



Pi'ofessor Molengraatf, formerly state mineralogist to the South 

 African Kepublic, discusses " the genesis of the diamond, and says 

 that the theory of the formation of diamonds during the ascension of 

 the blue ground from carbon borrowed from the carbonaceous shales 

 was, in his opinion, weak. 



In the Pretorian beds, as well as in the formations nnderlying these, strata 

 containing any notable quantities of carbon were nowhere to be found in the 

 Transvaal ; so that the conclusion might safely be drawn that the igneous blue 

 ground, in forcing its way from great depths toward the place where it was 

 I'ound, could not"l)orrow any carbon from the surrounding strata in order to con- 

 vert it into diamonds. 



Jn Bohemia a rock occurs which contains every mineral known in 

 the blue ground of Kimberley except diamonds. On my visit to the 

 Mining Academy at Freiberg. kSaxony, a few years ago, Doctor Stelz- 

 ner, professor of geolog}^, showed me two cases containing these min- 

 erals, and in every instance the Pohemian minerals corresj)onded 

 with those from Kimberley, except that the case of Kimberley min- 

 erals contained a few small diamonds which I had })resented to the 

 academy. 



Both the aqueous and igneous theories of the origin of the kim- 

 berlite have had able sup})orters, among those of the former being 

 Stanislas Meunier,'' M. diaper,'' and later Professor Garnier and Sir 

 William Crookes.'' The igneous theory is strongly supported by 



« A Monograph on the Diamonds at Rietfontein, near Pretoria, in the Trans- 

 vaal. 



& Composition et origine du sable dianiantifere du Du Toits Pan. Afrique Aus- 

 trale — Comptes rendus de I'Academie des Sciences de Paris, Vol. LXXXIV, No. 

 6, p. 2.50. Examen mineralogiiiue des I'oehes qui accompagnent la diamant 

 dans les mines du Cap de Bonne Esperance — lUilletins de TAeademie Koyale de 

 Belgique, 3d series. Vol. III. Xo. 4. 



c Note sur la region dianiantifere de TAfrique Australe, Paris, 1880. 



''A lecture before the lioyal Institution of Great Britain, ,Iune 11, 1897. 



