Idaho Springs siftings., 1902-12-20
WHAT is BEING DONE
In THE MINING WORLD
Secondary Enrichment.

Denver mining engineer, who is st
present engaged in making an exhaus-
tive examination of all the properties
owned by the Stratton estate In Grip
pie Creek. contributes an interesting
and valuable article to the current
number of the Engineering and Mining
Journal on Secondary Enrichment at
Cripple Creek" The question covered
by the article is one of the greatest i'm
portance, and opens up a vast field of
speculation for those interested in the
Cripple Greek district. If the we'll
known gold camp Is to produce other
metals in connection with it's gold
output at greater depth the life of the
camp is continued indefinitely. and
renewed confidence should naturally
result. The article in full follows:
The opening up Of deposits of gray
copper in the lower levels of some
Cripple Greek mines opens field of
mental speculation which may be of
profit to the future of the camp. Gray
copper is almost always n product of
secondary enrichment The gray cop
per of Cripple Creek is very rich in
gold, in most, if not all, of the places
where it has been found In the few
places where it has been developed it
shows very lair dimensions. The the
ory of the secondary enrichment of ore
deposits has been well substantiated in
the last few years by the very able ef-
forts of members of the geological
survey. and other eminent geolOgists.
Secondary enrichment with it's neces-
sary attendant secondary impoverish-
ment is so noticeable a feature of
many coppersilver ores that the i'm
poveriShed zone is absolutely worth
less, and the enrIcned zone is the only
part of the deposit having commercial
value.
The great Copper Queen mine at
Bisbee. Arizona. and the mines of Eu-
reka, Nevada. are conspicuous exam
pies of secondary enrichment. That
this same natural process has had
much TO do with the formation of gold
deposits is well known, but gold being
so very inert in ali chemical reactions
the influence of the forces which pro-
duce secondary enrichment are not.
as rule, so marked as to force them
selves upon the attention. Moreover,
in gold veins we generally have two
forces of secondary enrichment at
work, namely, mechanical and chem
ical. and the mechanical enrichment
is often more noticeable than the
chemical. The mechanical enrichment
takes place very close to the surface,
and the degree of intensity of the en-
richment depends entirely upon the
tineness of the gold and the porosity of
the vein. As erosion takes place there
is a tendency for the gold of the vein
to be carried by the surface waters
down into the underground water
channels and there lodged If the gold
is very fine and the vein very loose
this action will accomplish a very con-
siderable secondary enrichment near
the surface. The other source of sec
ondafy enrichment, chemical con-
veyance of the gold, depends on
so many different conditions that IL
would be a difficult matter to foretell
with certainty where it would be an
important factor and where it would
not.
I'm the Cripple Greek district it
would seem as though conditions were
ideal for both means of secondary en-
richment The veins in the upper lev
els are generally loose and porous.
The gold resulting from the decompo-
sition of the tellurides is in an amor
phous form. whic- is an ideal form
for mechanical conveyance. The early
attempts at milling these ores proved
this fact so conclusively that it was
d'SattrOuS to the mill owners. A rich
zone of oxidized ore bodies has fol-
lowed the inequalities of the mountain
surface with such persistence that
there can be but little doubt that sec
ondary enrichment by mechanical
means has p.ayed a very important
part in the formation of Cripple
Creeks superficial bonanzas Now, in
the last few months several bodies of
gray copper have been struck at
depths of l 200 to / 400 feet from the
surface, and these bodies are of fair
size and immensely rich. Can it be
that we are only just now approach
ing the true zone of secondary enrich
ment? The suggestion opens up fer
tile field for the Imagination. May it
not be that the bonanZas which at
tracted the attention of the civilized
world in the early days of the camp
are to be surpassed, possibly many
times over, in the gray copper zone?
II he fact that copper is almost en-
tirely lacking in the upper levels, and
that it is found in a secondary form
on the lowest levels associated with
gold would indicate that it had been
leached out above and precipitated be-
low, and the further fact that in its
present state it is rich in gold sug-
gests that it had a companion in its
migratiOns, and the companion is, of
course. the main end of all Cripple
Greek mining.
IF there is zone of secondary en-