120 



SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



according to the methods of crystallography, very difficult, and for this reason many 

 questions regarding the crystallisation of diamond are still open to debate. In 

 what follows, the most important general crystallographic relations will be dealt with. 



Fig. 31, a-i. Crystalline forms of diamond. 



while special features peculiar to diamonds from particular localities will be mentioned 

 under the description of these localities. ^ 



Observations on the crystalline form of diamond date back to the beginning of the 

 seventeenth century, many diamond crystals having been described by Keppler, Steno J3oyle, 

 and others. Rome de ITsle and Haiiy, the founders of scientific crystallography, were, at 

 the beginning of the nineteenth century, the first to correctly interpret the different forms, 

 and to determine the hemihedral development of the crystals. Great credit is also due to 

 Gustav Rose for his exhaustive study of diamond crystals made at a later date. The 

 results of his investigations were published in 1876 after his death by A. Sadebeck, who 

 added numerous observations of his own. 



Crystals of diamond belong to the cubic system, and, according to the views of the 

 majority of mineralogists, to the teti-ahedral -hemihedral division of this system. Certain 



