New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1879-08-11

cts6Iul quartz mining it4HEtHd tdp-lal 81 AuAl'"H
Of thousands Of dollars.
The second class Of gold mines found in the
Black Hls-quartz in slate, or between slate walls
is represented by the great "belt' above Dead
wood. on which tho mammoth mines Of the Halls
are situated. The country rock, that the rock Of
which the mountains are formed, is micaoeous slate
which has been thrown up at an angie Of about 5O''
Between tue walls Of this slate is a VEN Of brown
quartz containing free gold in small quantities, and
separated from the country rock each side by
layer If chloriuo slate often containing more gold
than the quartz itself. The vein is Of enormous
wIdth-ffora 40 10 $50 feet-but is frequently d.
yided by "horses" of slate OF large bodies Of that
substance extending into or across the vein. The
rock in these horses" is sometimes rich enough 10
work bat generally is quite barren.
There are two theories of the formation Of these
veins and while there seems to be sufficient ore in
all The large mines for present purposes, the future
Of these properties may depend in great degree
upon which of these theories proves to be the cor
rect one. The first is that advanced by Professor
Jenny the young geologist who was sent to explore
the Black Hills in 1879 for the Interior Depart
ment, and who is now q resident of Deadwood. he
holds that these lodges Of goldbearng rock are true
hssure veins" interamInated assures" be calls
them. that Is, assures opened between the layers
of the slate rock and not across the line oil stra5l
cation. The aurlcrOus quartz, he says, has been
formed by the water solutions which have come up
from below. lie accounts for the horses Of slate
in tie vein by lkenlng the cleaying OF the rock
to the splitting Of a piece of oak wood. When q
wedge is driven into it, particles Of the wood
cling from side to side across the opening made
by the wedge. So. he thinks. when the rock
was opened, bodies If slate extended across from
one wall 30 tie other, and remained in that position
when the aqueous solution from below came up
surrounded them, and deposited the gold-beaung
quartz. lie explains the fact that the slate walls
and horses cogtain gold by saying that the slate,
which had minute spaces between its layers soaked
up the mineral bearing fUid which in some cases
replaced tho particles of slate. As a rule
the impregnation Of the slate becomes less as
the distance from the wall of the vein in
creases. Believing the veins TO be true fssures
Professor Jenny supposes that they extend into
the earth for an indefinite distance, and
probably grow richer in their lower portions Pro-
fessor Jenny believes that after these veins were
formed the ocean covered what are now the Black
Hills. and that by its action it tore down the sur
face, scattering fragments Of the vein al over the
country. Evidences of marine action are easily to
be found in tie vicinity of the mines.
The other theory held BY several geolorsts Of
much learning and experience is that the vein
matter was precipItated from an aqueous solution
that covered 10. Their explanation and argument
Is this: The foOt-wa1 Of these veins is slate a
formation which everybody Knows IA Of aqueous
origin. The vein Of quartz deposited on this slate
parallel with its line Of qualification. Just as one
layer Of rock is deposited on another. Above the
vein we also find slate. and above that where it has
not been carried away By the action of the ele-
aIl If
These facts point couclusvely to a horizontal de-
post of the vein matter on "a slate bed The pre-
eyt8nt was probably oxide OF iron, and ii Is
therefore very natural that those ores containing
tie largest proportion Of oxide of iron should be
the richest B gold, they After all these de-
posts had been made, the hills were gradually
thrown up IN their present forms under water.
Ii the true assure vein Theory l. correct land IL Is
the one most generally accepted by the most eype-
renced mmeTS), then there 70 believe that
the ore extends far into the bowels Of the earth.
And even II the theory OF an aqueous deposit
precipitation Is accepted, the fields which these
deposits took place may have been so great that
when turned up upon their edges they may be
practically EexhausuDle. must defer descrip-
ton Of the great belt" as l have examined 10 IN
all the mines that have been ODened upon r. for
another letter.
The quartz veins between pOrphyry walls have
not beea sufficiently developed to make it safe 10
give an opinion IN regard To them. Some OF the
best mines Of tins class are situated IN strawberry
GuIcb, about seven niles east OF DeadwOOd, and in
some of them considerable bodies Of ore have been
found. In another year. when few mills shall
have been erected near them for tie purpose of
working their ores, and development has been
pushed urthcr more Will be known of their valns.
IL is an interesting fact that they have already at
tracted the attention Of the rich California miners
and capitalists VINO have developed the great
belt above DeadwOOd, and that II Is possible
that they may purchase one Of the most promising
oil them and see what II contains.
In many of the placer mines, a little below the
bed of tine stream Uut considerably above bed rock,
layer OF hard cement, consisting OF sand, gravel
and DOudcI,dnd carrying Tree gold held together ~
one hard, CUhglum"raje mass bY oxide OF IRON. has
been found. THIS substance has been a great Oh
stacio to CuCE miners on some claims. They had no
of crushing II % free the gOd and TO remove
il I'D order ~ get at the durlicrogs gravel beneath
was very expensive. On the hlll-tops which have
wIthstoOg best the action Of the elements similar
cement deposits have also been found, varying from
and nall 10 twelve aud eighteen feeU ID thick
ness Some Of these are very rich IN gold and Others
very lean. \ number OF mines have been opened on
the cement beds and are now working success
fully, while Others have already worked out their
pay ore. The rock In reduced IN the sane manner
as quartz by stamping aud amaigamatug. ce-
menr deposit may De- very valuable as long II
lasts and may bring 10 its owners large profits Dut
It's value depends entirely upon IT'S extent aud char
acter. Like placer lsnd II Is, IN fact. nothing but
a sodIted placer, 10 Will some day be worked out
aud become worthless. l have reason 90 believe
that an attempt now beng made to sell one OF
two Black Hills cement mines IN The East. aud !
have seen q prospectus sad ID have been prepared
tor tire NeY-1Jr market, IN which Uhs richness of
one Of these mines is described in the most glowing
terms with no ggeSCons chat the Is not quartz
vein. | nave not visited the mine myself.
and know nothing about It except that II Is a ce-
ment deposit and not vein. Very likely the ore
90 prospects ana mills as hlgn a Is represented
and possibly the quantity Of IL Is very great, but
no one ought TO purchase the stock surprising ne Is
buying into . true assure VEN mine. Ii lie does he
may get the value OF his money back and no may
lose a good part Of his investment
nave attempted in this letter only to give a gen
era idea Of the character Of the gold mines OF the
Black iillls. Hereafter shall describe some OF the
most important mines IN this and adjoining dis
trlcts. z. l. W.
MIDNIGHT WE6 THEE REPORT
GOVERNMENT INDICATIONS