Payette enterprise. (Payette, Canyon Co., Idaho) 1909-1935, 1915-03-11
A LETTER
FROM BRAZIL

d The following letter from Ralp
v. ThurstoH to his parents Mr.. ans
e Mrs. ]. S. Thurston of this city
J, Will prove Of interest as 1t describ
( es the quaint old towns and their in
:. dustries. The school of engineering
t which he describes is, We believe
/ the one with which Mr. Thurston il
, connected.
2 MORRO YELHo.
MORO Velho, which means "olt
hill", is little town about 400 mil
: es north OF Rio de Janeiro and
; about 10 miles from BelIo Horizon
te, the capital of the state of Minas
Geraes. 1t is one of the oldest set
Elements in the state as gold was
discovered there at an early date.
One mine is still being worked on
quite an extensive scale by an Eng
lish company and this, with the
mill that treats the Ore, furnishes
occupation directly or indirectly for
most of the inhabitants of the town.
This mine, the st. John del Rey,
was first worked in 1925 and has
been operated by the present COM
pany since 1885. 1t has the destine-
ton Of being the deepest god mine
In the world about 5000 feet verti-
cal depth from the surface and as
the altitude of Moro Velho is only
1000 feet, the lowest workings of
the mine are 1000 feet below sea-
level In spite of good artificial ven
tilation the lower levels are very
hot due to the great pressure Of
the rocks the temperature being
So degrees F. The vein is quite ire
gular in width varying from few
inches in some places to 80 or 40
feet in others. The value of the ore
is quite uniform, however, but de-
sreases slightly with the great
depth; the average value Is said to
be about $40 per ton
AS the ore comes from the mine
the cars, each holding about a ton,
are weighed separately after whi- n
the ore is dumped on what is known
as a 'grizzley-' heavy iron bars sci
parallel and about three inches apart
the finer pieces drop thru and the
large pieces fall on large revolV-
ing circular table where a half doz-
en- negro women pick out the pieces
of waste rock. The ore is then crush
ed in crushers and stamps until II
passes a so mesh screen Ca screen
having so wires per inch or SSOo
openings per square inch) after
It is washed on canvass covered tab
les and about rs per cent Of the re-
coyerable gold is removed. 1t then
soe. to large tube mills where Is is
ground as fine as flour and VIII
pass a 100 mesh screen, or one
having 10000 openings per square
inch. From this last grinding IT
goes to large tanks where it is agi-
tated with a solution of sodium cy-
anide which dissolves most OF the
remaining gold. The solution Is ILL
tered off thru large mechanical FL
ters and is then run thru boxes con-
tanning very thin shavings OF zinc
which precipitates the gold from
the solution. The zinc and gold
are then treated with sulphuric acid
or with caustic soda, either OF
which will dissolve the zinc and
leave the gold behind The gold thus
obtained, together with that from
the canvass tables, is melted and
cast into bars about three by five
inches and half inch thick. These
bars are not pure gold but contain
about 20 per cent silver, which is
with the geld in the ore;
the gold and silyenr are separated
by electrolysis after which they are
melted and cast into bars of pure
gold and pure silver.
About 500 tons Of ore are mined
and treated daily which means a
daily output Of some $4,000. In spite
OF the fact that this mine has been
worked for nearly 200 years there
is still enough GRE blocked out''in
the mine to last six years longer at
the present rate Of production, and
it is quite probable that the mine
will continue to be worked for at
least fifteen years longer.
oURo PRETo.
Ouro Preto (black gold) Is one
of the old mining camps of the state
Of Minas Geraes and was the capi-
tai of the state until about is years
ago. A narrow gage railroad runs
from the main line Of the Central R.
R. at BURNER a distance of about
forty miles to Mariana which Is /