Gold in British Goiana. 283 
The following extracts from Professor H ART'S t( Journey 
in Brazil" are suggestive : — "The diamonds of the Chapada 
Diamantina come from a conglomerate and sandstone 
which appears to be a tertiary rock. I do not believe 
that the diamond ever occurs in the real Palaeozoic itaco- 
lumite in Brazil, but that it is derived from the tertiary 
sandstones." He observes further "I am disposed to 
regard the Chapadas of Erere as the outliers of the great 
tertiary sheet which covered the great Brazilian plateau, 
and now lies unbroken over such an immense extent in 
the province of Matto Grosso. According to the obser- 
vations of Dr. R. P. Stevens and others, the plateau of 
Guiana is covered by an extension of the same great 
sheet." In confirmation of this latter statement we find 
Mr. Barrington Brown remarking in his work on 
the Amazon that the mountains of Erere and Maxira etc., 
are composed of beds of whitish sandstone identical 
with that of British Guiana. The Canga of Diamantina 
consists ot a conglomerate of quartz mica, and other 
components pasted together with red and yellow iron-clay 
and covered with the dark ferruginous shining metallic 
coat which gives to it a name. ESCHWEGE was inclined 
to consider itabirite as being occasionally the matrix of 
the diamond. 
Thus it will be seen that there is nothing in the 
minerological composition, or geological age of a large 
proportion of the rocks forming the surface of this 
colony, to militate against the opinion that they are in 
many respe6ls identical with the diamondiferous series 
in other parts of the world, and may be sufficiently pro- 
ductive of diamonds to make systematic mining for them 
a profitable industry. 
