The Yale expositor. (Yale, St. Clair County, Mich.) 1894-current, 1910-07-15


which is found suitable for the dia-
mond.bearing streams OF the Diaman-
tina district, somewhat resembles
placer gold washing. The process con-
sists primarily In digging out sand
and gravel. which are put into small
wooden bowls, each capable of holding
or 10 pounds. The native miners
then proceed In Indian file with their
loads to some convenient part OF a
river or stream, where they laborious-
ly wash out their material, gradually
getting rid of all lighter particles and
debris until the hidden diamonds,
whose specific gravity is 31s, reveal
themselves through their weight and
peculiar luster. Iron pans with small
perforated holes are sometimes used
TO hasten the process of extraction. A
modification of this plan, where a
considerable pit has been excavated,
consists in finding a curve In the riv-
'er some distance above, with natural
fall OF 20 or 30 feet, and diverting
thither part of the stream through
an artificial channel.
A different method of mining has to
be employed in the localities called
"chapadas," or plateaus, where dia-
monds are imbedded in compact, some
what resistant, conglomerates. A
small reservoir. or II necessary, two
or three reservoirs, are built, rude
dams are placed at various points
across the nearest available river, and
with the increased water power thus
obtained the conglomerates are washed
down ravine to the desired lower
level, where the process OF further
diamond extraction may be continued.
Primitive as are the processes de-
scribed. they have yielded in the past
one hundred and eighty years sur
prisingly rich returns. According TO
the best authorities, the total Bra
lillian diamond production, including
the extensive contraband trade prao-
tised during the Portuguese colonial
regime, Is estimated at 10000. 900
carats, or Pa metric tons. The total
export value of diamonds of every sort
from Brazil in 1906 is conservatively
calculated at about $5,000,O00.
One Of the first enterprises TO install
dredging and hydraulic machinery for
the extraction of diamonds such as
the alluvial diamantiferous deposits OF
the Republic require was the Boa Wis
Ia company. in 1899, formed In Paris,
with a capital Of 100000 francs, or
100000 Their mining concessions
were situated at Boa Vista, on the
north bank of the Sac Francisco river.
above the Falls of Paulo Alfonso, and
about 800 miles from the Atlantic.
The Brazilian diamond-bearing de.
posits so far discovered are all allu-
vial and surface, and they possess
many natural advantages over the dia.
mantiferous fields of South Africa.
which, as has already been explained,
are dry diggings,' requiring the most
expensive processes and machinery
and every device that human ingenu-
ity can invent for the successful ex.
traction of diamonds. In Brazil, on
| the other hand, the diamonds con.
| cealed can be easily extracted by
means of hydraulic and dredging ap.
I paratus. A network of rivers and
streams affords an unfailing and co
pious water supply and power. There
is no deep mining to be done, as is
the case in South Africa. Only very
small portion of the probable total
Brazilian alluvium has been explored
and the river gravels. except in the
reaches of only moderate depth, are
untouched. Moreover, these gravels in
many cases carry enough gold to pay
for dredging, and even. platinum may
be found.