The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1924-02-29
DEVELOPMENT Of
LOW GRADE ORES
ON THE MESAb|.
(By w. G.. Swart)

This paper is a discussion of the
use and beneficiation of low grade
ores rather than of the discovery
and development of new ore bodies.
That there is abundance of raw
material is without question. In
1911 the United States Geological
survey published an estimate that
the Mesabi Range contained thirty
billion tons assaying 35 per cent
iron or better, and 125 billion tons
of 25 per cent material. The fig
ures for the entire Lake Superior
region were 81 billion tons of 35
per ent and ACT billion tons of 20
per cent material. At the present
rate of consumption this would last
from 5000 to 5000 years. We
may therefore turn directly to the
methods of utilization.
History shows that all the older
metals were first recovered from
high grade, direct-smelting ores. As
these ores became scarcer and metal
lurgical methods were improved,
lower grades came into use, until
today almost all the copper, lead,
tin and zinc are won from material
that has been mechanically concen-
trated. The newer metals like
aluminium and magnesium are ex-
ceptions. So to some extent is iron,
but the great modern demand for
steel is bringing it into line with the
old, metals. ~,
Average Iron Content Declines.
When the Lake Superior district
was young the ore had to assay 60
per cent to SIS per cent iron to be
marketable at all. In 1922 the
average iron content had gone down
to so per cent. 1t would have been
the shipments of some four million
tons of washed ore whose grade
was considerably above the average.
This came from eighteen washing
plants on the Mesabi and Guyana
ranges. "a
In any consideration of the ore
reserves back of the great iron and
steel industry of the Central United
States it is almost impossible to
make statements covering the
Mesabi range alone. All the ranges
are involved, and while have no
desire to make this paper a riot of
statistics and curves, a few figures
must be given. T.
AS far as we can see now, the
Lake Superior region is to continue
to supply the iron ore for the Low
er Lake and Mississippi Valley
country, where our great iron and
steel industry is located. The open
ing of the st. Lawrence waterway
might bring the ores of Newfolnd-
land into competition, but these
ores are not higher grade than our
own.
Ore Production Peak Not Yet
Reached.
The demand for iron ore fuctu-
ates from year to year, but based
ON existing steel making capacity it
seems reasonable to say that today
the normal annual demand on Lake
Superior is for 100000 tons. In
1923 the shipments were 6O,000,OOO
tons. In the past this demand
doubled every ten years, but in
future such a rate of increase can
not be maintained. IF there shall
be no increase at all, Lake Superior
can stand the present heavy drain
for twenty to thirty years. Such a
statement does not mean, as is
often assumed when discussing the
life of the iron ranges, that the
last ton of ore will be gone in so
many years. but rather that because
of physical limitations the peak of
possible production will have been
reached, we'll within the period
named.
Curves have been plotted showing
the life history of several of the
great mining districts of the world
as we'll as many individual mines.
They are all much alike in form,
rising rather sharply to a rounded