The diamond drill. (Crystal Falls, Iron County, Mich.) 1887-1996, 1903-06-06

othAIfR1tA Va RtC~ A1hA VI AAh oNAt1tc
those just south of it are upper car
boniferous limestone. with lower car
boniferous Devonian and Cambiian
beds coming successfully to the surface
along the fault to the northwest.
Ore is usually found in large masses
along the contact OF the limestone
with the main porphyry mass. This
contact. however. has not been thor
oughly explored. and much the ore
along it consists largely Of low-grade
partly oxidized pryite. bikes and stills
of porphyry occur in the limestone at
various distances from the main
intrusive mass and these are almost
invariably associated with orc in tho
adjacent limestone. In some cases
large ore bodies, followed for n long
4 distance in the general plano OF the
bedding have been known 10 turn
down almost vertically alongside a
porpyry dixie. Fissure in the lime
stone have also undoubtedly influenced
the distribution 70 the ore.
The ore bodies that have thus far
proved workable have resulted from
the operation of later processes of con.
centration acting upon the original
pyritic ores. The occurrence of the
chalcocite is closely related to the
general process of oxidation, and this
mineral has plainly been formed by
| kn oe naoaanHintr gplf,t ion
upon lean pyritic ores IL is probable
that at least part Of the chalcopyrite
is ascribable to the operation of the
same agency. There is an observed
connection between good ore and per-
meability to downward moving solu-
tions. Such pyritic ore as proves
profitable is soft and crumbling, and
usually shows upon close examination
interstitim sooty material that is
probably anonymous chalcocite.
The lower limit Of oxidation Of the
ores is very irelguar and is apparent
ly uncontrolled by any constant
ground-w level The statement
may be yentursd that the spector Of
+, the lower lime has hitherto lad an
, undne influence in restricting pros
pecting u horizontal planes There Is
certainty a reasonable hope o. finding
{ ore bodies n tire Deyonian and Cams
brian limestone beneath the masses
Chat have been 70 protiably worked in
Che uverlying carboniferous beds
A little less than half mile south.
east OF the center Of town the fault
} encounters mass 81 latered granite
porphyry and as simple fracture
+ disappears. This porphyry which
forms Sacramento Hill Is well known
local landmark, il very irregular
mass about a mile in diameter It he's
invaded the pre- Calnbrian sctistg on
the northeast and the upper carloni.
ferrous probably also tho deererlyins
older Paleozoic beds on the southwest.
The available evidence indicates that
the intrusion of this prounyry took
place after the diHlocation of the IT,
yaded rocks by the great fanlt The
latter probably continues TO the south
east Of the porphyry mass, but il j.
concealed in this direction hy the
Younger Cretaceons beds The
Palezoic beds forming tho faulted
syncline are not merely Hexed, but are
cut ~ many faults, some Of them cf
considerable throw These faults are,
as far as seen, of the normal type
The ore occurs cry irregularly as
large masses within the limestone
The horizontal extent of these bodies
is usually much greater tnan the YER
teal They are rudely tabular in
form and lie generally parallel to the
bedding planes of the limestone
AS a rule the important ore bodies
have been found within a distance
of /, 900 feet of the main porphyry
mass or Of the great fault assure just
northwest of the porphyry. In the
Car workings OF the Copper Queen
mine. partly under the town of Bisbee
ore bodies have been worked from the
surface down to depth of about 400
feet, but toward the southwest the
bulk Of the ore occurs at increasing
depths In the Calumet & Arizona
mine, ab-ut 35 90 feet south of the
Gar, no large ore bodies were en-
cuuntered until the shaft had penetrat-
ed about 500 feet below the level at
which the first ore body was dis
covered on the Copper Queen claim.
The ore thus occurs at increasing
depths somewhat less rapidly than
would be the case did it correspond to
a definite straitigrapnic horizon.
With the exception of the extreme
western part of the Copper Queen
mine, all Of the productive and inn
portant workings in the vicinity of
Bisbee are in the carboniferous lime