~ 
446 O. A. Derby—Oceurrence of Gold in Brazil. 
is at present confined to one of the thicker beds of quartzite 
which is considered the richest, but very good tests were ob- 
tained from the black gneiss and also from loose masses of 
reddish half-decomposed rock much more feldspathic than 
that in contact with the quartzite bed. Considerable iron sand 
was obtained in all these tests. 
The washings at Sado Gongalo lie on both sides of a small 
stream that flows near the base of the Serra de Sao José and 
parallel with it. On the town side a broad belt over a mile 
as been almost continuously washed, and it is said that 
other washings make with these an almost uninterrupted belt 
of washed ground as far as the mouth of the stream in the 
distance of several miles along the strike. Although the de- 
composed material has been very generally washed, traditions 
speak of richer streaks, and there is some reason for supposing, 
from the few experiments made, that the more quartzose an 
ferriferous portions are richer than the generality of the mass. 
The proportion of gold shown by a single panfull of dirt 1s 
very small and the average richness must be very low. ’ 
informed that some recent tests on a measured quantity of dirt 
gave about fifteen cents of gold per cubic meter. 
wing to the extensive decomposition, there is considerable 
difficulty in obtaining unaltered specimens of the rock in con- 
The mica is abundant in fair-sized black flakes; the quartz 1s 
in small well-formed crystals and is the least aed Mle in- 
gredient, while the feldspar, which is the most abun 
is white, a large proportion of it being plagioclase. In the 
were found on examining a hand specimen. In view of the 
almost constant association of pyrite with the gold of the cen- 
tral and northern parts of the province in the auriferous schists, 
