The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1876-07-22
Our @lio.
Lake Superior Copper Mines.

. pure coppct nus Si'Sh WIG HithihS uibtflCtn
Of Lake Superior worldwide reputation
The first masses brought from there ex.
cited great attention, and directed the no.
lice of the mining world to tho few par
iicular mines from which they were taken.
il may not now be generally known that
hearty all the veins which are worked, and
(which cut across the trap ridge, contain
mass coppers and that large masses are
continually being raised from them.
The largest continuous mass which has
been taken out was probably that from
he Minnesota in 1857, which is variously
tated as weighing 420 tuns and 40 tuns.
its length was about 45 feet, its breadth
b hight % feet, and its greatest thickness
feet. All such masses are very irregu-
hr and ragged in their form and thickness,
hnning out gradually from foot to few
nches, and struggling through the vein
hntil they connect with other large masses.
This was the character Of mass found in
Die Pheuix mine, one of the oldest on the
,ake, which mass altogether weighed some
700 tuns. But this was really series of
passes more or less connected by strings
b metal, yet no one large part of it weigh
n, singly, over 200 tuns. A similar sc
ies of masses, weighing about 600 tuns,
as extracted from the Minnesota. Some
n the Phoenix masses were four or five
pet thick Of solid copper. The Cliff mine
as yielded masses weighing from 100 to
DO tuns in one piece. One of 40 tuns
Fns taken out this year, besides numerous
bocks weighing from to tuns. This
hinc and the Central are now yielding
pass copper in abundance.
1t is of course impossible to pick, or to
bill, or to break out such huge masses of
bid metal, when they are found by drift
iog upon the course of the vein. The
nethod is MS follows: The miner picks
~, or excavatcs, narrow passage or
shamber upon ono side Of the mass, laying
bare as far as possible over its whole
snrlace. 1t is usually firmly held by its
lose union with the vein stuff, or by its
Irregular projections, above, below, and at
DC end. If it then cannot be dislodged
~ levers, the excavation of chamber is
epmmenced behind the mass, and this ex-
walton is made large enough to receive
nom five to twenty or more kegs of pow
der. In one instance, in the Cliff mine,
. charge Of 81 kegs Of powder threw down
700 tuns of copper. Bags of sand are
xeed for tampiug, and the drift is closed up
By barricade of refuse and loose dirt.
Aiter such blast the drift is, of course,
chnrged with foul air, and it cannot safely
ln entered for hours afterwards. II en-
<trcd too soon, men lose all strength in
heir limbs, and fall down.
The huge masses of copper dislodged in
IBIS way are too large to be handled and
got to the surface. They have to be cut
m. The copper cutters are called in,
md the mass is marked off in squares or
t|ocks of suitable size Copper cutting is
distinct art, and requires considerable
ill and experience. Ordinary miners,
however skillful they may be cannot cut
II copper without long training.
The tools are simply narrow chisels aud
hiking hammers. The chisels are shaped
Ike the parting tools of turner's. They
W made of fiat bars of half inch steel,
bout 2 inches wide and Is inches long.
hey are chamfered each way like cold
4hiscl, to form the cutting edge. This
2lgo is made little longer than the thick
1ess of the bar. The cutter holds the
ehisel and two men strike it. A thin slice
q chip of copper is in this way cut out in
harrow channel across the mass Of cop
~. The operation is repeated until the
tarrow cut, but little over half an inch
ride, has been carried through the mass.
be chips cut out 10 this way are long
narrow strips of copper only about half as
|qng as the groove from which they are
ken, the metal being condensed aud
>hickened by the force of the blow.
This work is necessarily slow and tedi-
q1s, and it costs sl2 per square foot by
ontract. At this price, the cutters make
~ per day.
Il is inconvenient to handle masses
Heighing over TONS Such masses, when
listed, are landed upon very strong plat
1rn trucks, and arc then dumped in the
Qck house upon a large pile Of dry pine
rs. When considerable number of
1|asses has. accumulated, the logs arc fred
vi the whole pile is heated to redness,
the purpose of loosening the very con-
aerable quantities of vein stone which
II enclosed in the ragged cavities. This
<ain stone consists chiefly of calcite; and
1[ler cooling of, It is so much softened
Ihat the greater portion can be knocked
~ by pounding upon the copper.
The masses are then marked, numbered,
VA recorded, and are shipped to the
e6clting works, where they are melted
own in reverboratories.
The Scientific American says; "a few
@Eops Of carbolic acid in pint Of water