O. A. Derby—Occurrence of Gold in Brazil. 445 
thin mantle of transported clays at the top, the greater part of 
the walls and all the bottom being of jeanne gneiss which 
is evidently im situ. The comparative rarity and insignificance 
of the quartz veins is equally surprising, and when they occur 
there is no evidence of their having been followed in prefer- 
ence to the enclosing rocks which have been worked away in 
mass. Indeed the veins are said to be generally barren, though 
that this is not always the case is proven by one of the mines 
at Sao Gongalo where a little work has been recently carried 
on along a face twenty feet or more in width traversed by a 
small vein which affords a richer streak. Some of the hills, as 
that of the Cata Funda at Sao Gongalo, have been worked in 
strike seems to be about due east, with a dip of 30° to t 
south. A small vein of pegmatite traverses the beds. Mining 
