290 The American Geologist. November, i898 
the copper has been precipitated in the granites or in part of 
the Hme not within reach of the iron. It may be that the ac- 
tion of the air-bearing water near the surface tended to Hberate 
sulphurous oxide and that an iron solution thus formed in 
the vicinity of the ore of iron produced the necessary condi- 
tions for precipitation, very much as they are supplied in cer- 
tain leeching plants for the treatment of copper. 
On the east side of the mountain near the axis, the lime 
is much tilted and is also disturbed in the direction of the 
strike of the range. In fact, the disturbances are of the most 
profound nature, yet the dip in general is sharply to the east 
and the limestone is minutely veiny. These veins are filled 
with fluorite, barite, quartz, and calcite and may also carry 
certain, or rather very uncertain, quantities of galena and. in 
some instances, wulfenite.. One or more faults parallel to the 
range repeat the strata toward the top of the formation in the 
successive foot-hills to the east and in these the metamor- 
phism has been less intense and the veins are not quite so nu- 
merous. The larger ones cross the strata in, or nearly in, 
the plane of the dip and are sometimes quite large and in such 
cases often carry large quantities of galena in a barite gangue. 
In general, however, the veins give of¥ "feathers" extending 
for fifty to seventy-five feet and these collateral veins are quite 
as likely to carry lead as the main vein so that the total amount 
of ore is difficult to recover. The commercial concentration 
of ores rich in heavy spar at a distance from water and fuel 
becomes an economic problem of as much difficulty as 
interest. 
The time may doubtless come when nature will accom- 
plish the concentration of the lead in much the same manner 
that it has done it in the Magdalena mountains and elsewhere 
where the sulphide, after having been altered to the sulphate 
is precipitated as a carbonate. That this process is in progress 
is shown by the fact that in the more exposed parts of the 
workings upon the veins the galena is quite extensively re- 
moved, and in parts not removed it is partly changed to sul- 
phate. To determine in advance the secret chambers where 
the percolating waters will find the conditions for the repre- 
cipitation of lead is beyond our power and this legacy to the 
future must be left to the future to recover. 
