The Barre daily times. (Barre, Vt.) 1897-1959, 1913-06-03
HOW ORES ARE
ENRICHED FOR THE
USE OF MAN
Natures Processes Described in Report
by United States Geological
SURVEY.

As originally deposited, deep in the
rocks, many of the familiar metals, es-
pecially copper lead, zinc, silver, and
quicksilver, exist as sulphides--that is,
as minerals composed OF one or more
metals chemically combined with sui
phur In such original or primary de-
posits the generally worthless iron sui
phide, pyrite, is likely to predominate,
ishile the more valuable metals may be
present in quantities too small to be
proftably extracted
| In the course of geologic ages, how
ever, as the land wears down under the
ceaseless attack OF weather and running
water, the primary ore deposit, with its
small proportion of valuable metals, is
itself exposed to the forces of disinte-
grafton and decay that are operating
over all land surfaces on the globe. Some
constituents of the disintegratng ore
are. carried away in streams; some are
blowa away by winds; and Others, par
ticalarly some of the metals, are dis
deed and carried by percolating rain
water down into the earth. These metal
charged solutions, coming into contact
with the sulphide minerals in the rocks,
have the chemical property of trans
forming these sulphides into Others more
valuable to man. Thus solutions carry
,lg copper and coming into contact with
pyrite, which Is a mineral compound of
sulphur and iron, abstract some of the
iron and leave copper in its place. The
bright yellow, beautiful but generally
useless pyrite may be changed, for ex-
ample, to the less brilliant dark |
gray but far more valuable min
eral chalcocite, sulphide of copper. |
This natural chemical concentration,
whereby, as the exposed upper portion |
Of an ore body decays and is removed by |
erosion, its valuable constituents are in |
large part carried down and added to |
the portion that remains, is an eXeep- |
tienally important process and one that |
has played an essential part in the for
nation of many large and highly pro-
dnctive bodies of ore.
by American Biologists.
Growing recognition of the over
Importance of enrichment in
the formation of sole of the largest
copper deposits OF the world dates from
the year 1900 and is due chiefly TO the
work of American biologists. A recent
publication of the United States geologic
-dl SURVEY p-'f tHtititd ut
Enrichment Of Sulphide Ores. by w.
H. Emmons, is devoted to the descrp-
ion and discussion of this process. The
roiume which is intended to bring to-
yether all the information at present
lvailsble on downward sulphide enrich
uent, is diyisible into two parts. The
irst part deals with the various eondi-
ions, such as climate and porposity of
". "a. al. l
ess and with the physical and chem
Ca principles involved. The second
a.t reviews briefly the available knowl-
dye of North American mining districts
n so far as this knowledge bears on
he problems of enrichment. The chem
st-y of enrichment is very fully dis
used in connection with the various
Minerals found in ore deposits, and the
tulents of ore deposition will find the
ook invaluable as a summary of what
known ON the particular subject
-,ated and as a guide to the literature
nat relates to il.
Valuable Report Can Be Had Free
The present publication. like Clarks's
Data of Geoehemistry," bulletin 491 OF
ie L. $. geological survey, illustrates
!. tINAN NV bthk uAdNt Ant
|, bring together, for convenient refer
Ice by busy men. data now scattered
u only through its own reports but in
her publications also. Such volumes.
,wever. are not mere computations.
he previously published material is en-
,hed BY new observations and is illu-
mated BY discussion in the light Of
e latest scientific knowledge.
The Enrichment of Sulphide Ores
illetin $50, may he obtained free on
lplication to the director. United
ates geological survey. Washington.
c. The demand for the second edi-
N Of The Data Of Geochemistry" has
en- so great that i was reprinted last
ar, and the reprint has recently be-
me exhausted. Another edition will
issued by the survey during ths pres
! year.