258 SCIENCE PROGRESS. 



diamond and carbonado (a black amorphous modification 

 similar to that found in Brazil and used for rock drills). 



It is interesting to note in this connection that Norden- 

 skiold had observed one piece of the Ovifak iron to be so 

 hard that it could not be cut or worked, and in view of 

 the constitution of the Canon Diablo meteorite it seemed 

 possible that this might also contain diamond ; it was ex- 

 amined by Moissan, who found no diamond, but an equally 

 interesting- result was obtained, for the iron was found to 

 contain sapphire, to which no doubt the hardness is due 



Taking all the above observations into account, it is 

 more than probable that the blue ground of Kimberley may 

 be the original matrix of the South African diamonds. 



Now a recent experiment tends to confirm this view ; it 

 has not only been found that microscopic diamond, graphite 

 and carbonado are disseminated through the blue ground, 

 just as they are in the molten iron of Moissan's experiment ; 

 but further, that under the influence of high tempera- 

 ture and great pressure the blue ground itself may be 

 made to corrode, to etch and to redissolve the diamond 



(21). 



The general tendency of recent research is to suggest 

 that several other metals and metallic compounds whose 

 origin is particularly doubtful may have crystallised out of 

 basic igneous rocks. These very questions have attracted 

 much interest among petrologists who have endeavoured to 

 ascertain how rocks of varying composition have solidified 

 from one and the same subterranean magma by a process 

 of successive segregation. 



Vogt has approached the subject more from the minera- 

 logical and metallurgical point of view. Two years ago he 

 showed that in all probability the iron ore deposits of 

 Ekersund and Taberg have been separated by concentra- 

 tion from basic igneous rocks. In the Ekersund-Soggen- 

 dal district the ore is an ilmenite-norite dyke, occurring 

 in a labradorite rock ; at Taberg the ore is a mixture of 

 titaniferous magnetite with olivine and a basic felspar, 

 which is a concentration patch in an olivine-hyperite (22). 



