MINING GEOLOGY 
337 
that is removable in the same way as the disseminated copper at 
the great camps of Bingham, Chino, and Inspiration. This 
amount is equivalent to the entire present world output of gold 
for a period of one hundred years. It is the production of this 
country at the existing great rate for more than five centuries. 
For more than a quarter of a century the problem of the 
primary source of the metallic ores has formed the most prolix, 
many-sided and bitterest controversy that has ever been recorded 
in scientific annals. Out of this seeming futile and academic 
debate emerges what may prove to be the greatest and most suc¬ 
cessful mining venture of all history. That the close of this dis¬ 
cussion should come so soon after the great World War, that it is 
really a direct consequence of the war, and that, in the economy 
of nations, it appears as far-reaching in its potency as any effect 
on the battle-field tending to eliminate world dominion by any 
one people, are themes wholly unexpected. Yet, commercially, 
nations may suddenly and entirely have to get off that gold ba*sis 
which has been: so long, so universally and religiously regarded 
as the foundation stone of all sound finance and, indeed, of civ¬ 
ilization itself. 
Keyes. 
« 
Origin of Bast Mesabi Magnetic Ores. The iron ores of the 
eastern part of the Mesabi Range are mainly magnetite. Since 
this magnetite has been altered in a few places to the ferric iron, 
producing secondary hematite ore-bodies, it is probable that that 
magnetite may have been the chief ore mineral all along the 
Range before weathering. 
Peculiarities of the bedded and banded structures, the miner- 
alogic composition, and the normal and probable chemical trans¬ 
formations seem clearly to indicate a primitive sedimentary origin 
of the ore beds. These are features which are so plainly manifest 
on the Mesabi Range that they give clue to the process involved 
in other districts where the several factors are more or less ob¬ 
scured. 
It is now well known that cherts and the several iron-bearing 
layers are commonly precipitated from solution from ordinary 
phreatic waters and form beds of notable extent. Solution of 
the silica of the cherts may have been facilitated by the presence 
