204 THE GENESIS OB^ THE DIAMOND. 



Professors Lewis," Molengraaff",^ and Stelzner.'" M}^ o\\n opinion is 

 tliat the aqueous theory is the less assailable. 



Concerning the origin of the blue ground, assuming that it is not 

 the original matrix of the diamond, I find the following weak points 

 in the igneous theory : 



1. As already observed, it is impossible to account by the igneous 

 theory for the water-worn bowlders found in the blue ground. 



2. The experiments of Herr W. Luzi,'' of Leipsic, in the produc- 

 tion of artificial figures of corrosion upon the surfaces of rough dia- 

 monds, are most interesting in the light which they throw on the 

 crystallization and the probable matrix and genesis of the diamond. 

 Until lately the only appearance of corrosion uj^on the surface of 

 rough diamonds was the regular, triangular, negative pyramids 

 which woi'e })roduced through heating the diamond in the open air 

 or under the oxygen flame. 



Herr Luzi discovered that the breccia (kimberlite) from the South 

 African mines when in a molten condition possesses the property of 

 absorbing the diamond or of changing its shape. 



The following is a translation of the description of his experiment: 



A small quautity of blue grouud was melted in a crucible placed in a Four- 

 quinon-Leclerq furnace at a temperature of 1,770°, which was the highest tem- 

 perature attainable. A diamond with perfectly smooth natural faces was sub- 

 merged in this molten mass. A further quantity of blue grounct was added to 

 the contents of the crucible until it was completely filled. A tightly fitting 

 cover was placed on the crucible, which was again exposed for thirty minutes 

 to the greatest heat attainable. When the crucible was cooled the diamond was 

 removed and found to be covered with irregular oval and half-round grooves of 

 various depths. In one experiment the diamond was found to be deeply eaten 

 away on one side. 



Some of these partly alisorbed diamonds upon which Herr Luzi 

 experimented are deposited in the mineralogical museinn of the 

 Leipsic University. 



Owing to the cost of the material to be experimented upon, how- 

 ever, Herr Luzi was unable to determine positively what chemical 

 action took place during the time the diamonds were heated in the 

 complicated silica-flux. The fact that diamonds can be absorbed 

 by being placed in molten blue ground tends to prove that the blue 

 ground was not thrust up through the earth's crust in a molten state. 



If the diamond is unable to withstand the corroding influence of 



oThe Matrix of the Diamond, Henry Cavill Lewis, at a metting of the British 

 Association at Manchester, August, 1887. 



6 The Occurrence of Diamonds at Rietfontein, G. A. P. Molengraaff. 



c A lecture by A. W. Stelzner before the Isis Society, in Dresden. Saxony, 

 April 20, 180.3. 



<i Ueber kiinstliche Corrosionsfiguren an Diamanten, Berichte der Deutschen 

 Chemischen Gesellschaft, XXV, p. 2470 (1892). 



