Amador ledger., 1901-03-01


on the south, and is in many respects
similar to it geologically. After an
idleness of about seven years, opera
lions were resumed in June last, and at
this writing, June 10TH the mill is
about ready to start. 1t is said that
good ore is being found at the north
end OF the mine
SOUTH KEYSTONE CONSOLIDATED
MINE.
This is half mile south of Amador
City. adjoining the South Spring Hill.
1t is in the prospective stage.
KEYSTONE NINE.
This is at Amador City, and is one Of
the most extensively developed mines
in the State. There are probably not
less than 10 miles of underground work.
ings in this famous old mine, but all
work at present is confined to points
above the l000-foot level, although the
shaft is 1915 feet in depth. The for
nation at the Keystone Mine consists
OF diGbase tuff, tufaceous states and the
clay states of the Mariposa beds, the
latter lying west of the principal veins.
To the west of these clay states, massive
diabase is again found. The principal
veins, however, are those occurring in
the tufaceous states. The main vein
occurs along fault plane, which has a
variable dip from 35 10 So degrees to-
the eastward and extending more than
1000 feet in a remarkable straight
course On the hanging-wall side of
this fault plane occurs immense masses
of diabase material and quartz, which
in places is more than 100 feet in width.
Considerable portions of this constitute
payable ore, although there are large
quantities which it will not pay to mine.
This great massive vein forms the
hanging-wall of a banded slaty vein,
which has produced large amount of
pay rock south OF the main shaft. Be-
tween the 400 and 800 levels on this
vein an immense stOpe covering a.
superficial area of 10000 square feet has
been cut, the vein in places being %
feet in width. There are few bers
and but one or two pillars in this great
stope, which has been open for years,
which indicates how well this ground
stands without artificial support.
This isprobably the largest open stope
on the Gold Belt. This was being filled
as rapidly as possible during my visit,
in order that the large amount of ore
known to lie in the overhanging $50
called) wall may be mined without
danger. On the hanging-wall side of
these veins is a greensboro formation
several hundred feet in width, through
which a crosscut has been run from
neigh boring gulch. The great quartz
vein lying in the hangingwall side of
this zone is from foot to more than
100 feet in width when measured at
right angle TO its dip. 1t is made up
of great lenticular masses of quartz,
brecciated quartz and diabase, having
interior assures or planes running
nearly parallel with the strike of the
vein. These are usually referred to as
walls. Some OF these masses are built
up by the splicing of the lenses. On
the SO0-foot level, and few feet dis
tant in the east wall of this vein, is an
2 interesting though small vein in reef
of pyritic, black tufaceous slate
Through the center of this reef is
found small irregular vein of quartz,
with small gouge and with numerous
fat branching seams. The occurrence
OF arsenical iron sulphides is a marked
and persistent feature of this little vein,
but more interesting feature is the
occurrence of pockets of gold, ranging
ia value from few cents to over hun
dred thousand dollars. The latter was
obtained between the 800 and 900 levels.
Within the past year, Mr.. w. A.
Prichard, the superintendent, has dis
covered number of good sized gold
pockets in this vein. On the 600-foot
dixie OF diabase intervenes between
JIG Rr0db IudSSIN0 N0lu anu bu0 pOCh6G
vein above described, while on the 900
foot level, about 200 feet farther north,
the diabase and reef of pyritic slate are
passed through before the great vein is
encountered. Arsenical sulphide was
also discovered on the 900-foot level, in
this vicinity. Although no pockets
haFe been found on the 900-foot level,
or below it, the indications are that the
pocket vein is older than the great vein
cutting across it, and that the pocket
shoot may be found from the 900-level
downward in the foot-wall of the great
vein. In the large vein are found the
widest Slopes in the mine. West of
this are two veins, separated from each
other and the great vein by varying
widths of tufaceous states. These veins
were also extensively worked in former
days. A careful and detailed study of
the keystone Mine would undoubtedly
furnish material for book much larger
than the volume in which this descrip-
tion is found.
BUNKER HILL MINE.
1t Is II miles north of AmadQr City,