Diamonds in California. — Turner, 191 
of contact metamorphism induced by the intrusive pegmatyte. 
Derby is inclined to think that the diamonds have come from 
the schists along the borders of the pegmatyte dikes and not 
from the dikes themselves. In other words, he appears to re- 
gard it possible that the diamond is a product of contact-meta- 
morphism. Moreover, he states that no rocks of the perido- 
tyte series have been found in direct association with the dia- 
mond-bearing beds at any point in Brazil. He lays some stress 
on the occurrence of tourmaline and disthene in fragments of 
schist in the South African peridotyte-breccia. Disthene is 
characteristic of schists, and tourmaline often so; and, as de 
Launay states that there are schists mingled with the lower 
quartzytes in the mines of South Africa from which the schist 
fragments in the breccia were probably derived, Derby sug- 
gests a possible analogy between the South African deposits 
and those of Brazil. He considers that in order to bring the 
Kimberle)' and Brazilian modes of occurrence into line as fa- 
des of a single mode of genesis, it seems necessary to put 
aside the idea that the recent interesting experiments on the 
artificial production of the diamond afford a solution of its 
terrestrial origin and also that the Kimberle}' type of rock 
and mode of occurrence are essential features, Derb\' would 
thus suggest the origin of the South African diamonds in 
the underlying schists as a result of igneous intrusions, a 
very unlikely hypothesis in light of the investigations of 
Lewis, de Launay, Crookes. Moissan and others indicat- 
ing the deep seated origin in molten material. It is 
regarded as certain by Derby that the Brazilian diamond 
must have had a different origin from that now ascribed to the 
South African occurrences. 
