New-York tribune., 1899-07-16
DEEP GOLD MINING.
REFRACTORY FEATURES TO FREE MILL
ING PROPOSITIONS OVERCOME.
HUNDREDS OF ABANDONED MINES IN cA1JFoR
MA STARTING INTO oPERATIoN-IMMENsE
VALUES DISCOVERED AT GREAT DEPTHS


Berkeley. Cal July s.-The success Of
the recent operations in the Gwin Mine. in
Calaveras County, Cal, has been a signal
for the starting into action Of not less than
two hundred mines which heretofore and
Tor periods as long as twenty years, have been
smut down, the owners believing meanwhile that
the ores Of the properties were worked out and
that the mines were therefore worthless. This
most important mining revival which even Cali
fornia has ever experienced occurs upon what
has often been called and now is determined 10
be the most remarkable feature Of economic
geology in the world. Imagine vast slab Of
quartz, milky white and glstening. from fifteen
to three hundred feet thick on its surface edge,
reaching down in the earth to infinite unex-
picred depths, and running continuously for one
hundred and fifty miles, and you have an idea Of
what the mother lode is like. In some past geo
logical time there was a great lateral split in
the surface Of the earth. and into this crevasse
ran hot waters heated al the furnaces Of the
earths interior and these carried silica in solu-
tlon and along with it gold and other metals in
soluble form. These were precipitated in the
cleft, the water dried out and there was left this
enormous ledge Of ore
\ feature Of the ledge however. is that it does
throughout its course. but the pay areas lie in
streaks being from five to forty feet in length
along the ;rend Of the body and Of width equal
70 the thickness of the slab. The entire mass of
tho body does assay but it shows only from -
to - cents TO The ton: it is upon these streaks
lenses Of mineral that the mines are placed. and
w and down The lode. through the five counties
which it .-reads there have been thousands Of
-l,r Il
twenty-five claims have been patented and
mines put into operation.
OLD MINERS MIsLED
When these mines however. reach depth of
about four hundred feet they encounter
stratum Of dense tough. igneous rock called
greensboro This zone Of material is entirely
barren of mineral and the old miners thought il
marked III. bottom of the veins tn lode got the
reputation Therefore. Of containing rich pay
streaks tat very shallow. and hence. unless th-
surface prospect showed we'll it was not ad'isa-
bic 20 undertake its Development With depth.
too sulrhurets came into the veins. and these IN
the old davs we're ? refractory feature to a free
milling proposition and hard To- work Twent}
years ago il cost from SO 70 SO tor go srne.t
sulI hurt =. nov. through the superior mechanics
Of conc -ntrat.ng-that is of eliminating al the
only IN, metal ana 10y The further process OF
treating with cyaNiGe-sulphuret can be- wc-ked
at from &i 20 81 a tor and rock which Will run
S5 in sulphIrets and & IN free gold can be- made
10 pay handsomely.
The gr-.nstone body having come INTO th-
bottom of most of the mines on the lode. there
was a general suspension Of operations which
made the district to a large extent abandoned
Millions Of dollars worth Of mills and machin-
cry lay idle rusting and rottng: underground
workings became flooded, and the mines were
little else than dark pits Of water there We're
svellinss and burstincs Of timbers. cavinCs in
Of material and general state az obstruction
and ruination Of hundreds Of properties. When
work was started on the GWin il was decided 20
leave the ola shafts entirely and 60 some wards
distant on the surface Of The lode and sink
straight down with the view Of catching tn
vein AT about loo feet. il was known 10
lead obl.cu-.y and not vertically into the earth
The mine had had a curious history. i was
owned bv Senator Gwln. whose family lived IN
Washington. they took out about 5000" d
year from the mine which sum they spent roy
ally until they had tnus consumed about
SGD0nr0 Then the property shut down ana
hecarne conraratively worthless No mining
man in san Francisco could be found 10 touch
II. only after years of effort was q company
cot together to resume operations, they took
the property at S1200t0 and spent $l"J"" N
opening it, The confidence which they had IN
their Undertaking was expressed by the bold
ness Of their executions. They sank a three
commandment shaft. the size Of an ordinary
house straight on TO the vein This was tapped
some hundreds Of feet below the bottom Of the
old workings. in which there lay as in a YES