286 The American Geologist. November, i898 
size which run about at riglit angles to the strike. These veins 
are numerous and occur at irregular intervals of a cjuarter to 
half a mile or more, and are so conspicuous that a number 
of them can be seen from the plain as depressed or elevated 
bands crossing the strata. The thickness of the veins varies 
also' but many of them are from five to twenty feet thick and 
are filled with the most diverse materials. Some are silicious 
while others carry fluor spar, calcite, siderite, baryta, etc. 
While the veins can be traced to the contact with the granite 
they do not penetrate it, or if they do, it is only in the form of 
a narrow fissure. It would appear that the flexure which pro- 
duced these fractures had more effect on the stratified than 
on the metamorphic rocks or that subsequent warping chiefly 
afifected the upper series. At the juncture of the Carbonifer- 
ous limestone with the granite there is often a thin band of 
red sandstone which has served to catch the leechings from 
the entire series above. Thus it happens that there has ac- 
cumulated a band of haematite at this contact which is some- 
times quite pure by substitution, but, in the majority of cases, 
is simply composed of a coating of the oxide covering the or- 
iginal quartz grains so that, when broken, every individual 
grain of the apparently oolitic ore is found to contain a quartz 
nucleus. Mining men have been deluded by this appearance 
into the attempt to use such material for iron flux; actually 
adding a rock with about 80 per cent silica to an ore requiring 
iron to assist in removing the excess of silica. 
A very hasty glance at the situation is sufficient to ex- 
plain the method of precipitation and segregation of the coo- 
per ores. The latter consist of copper glance, malachite, cup- 
rite, and, in fact, nearly all the common ores of copper mixed 
with siderite and haematite and gangue matter. The sul- 
phides of copper and associated silver must evidently have 
come in from below, rising possibly, in the circulating water, 
and it is equally plain that the iron band has accumulated 
by leeching from the superposed strata. At the lines of inter- 
section and in the presence of air the precipitation has taken 
place. Comparatively little of the sulphides has collected be- 
low the contact (iron) zone and very little has passed beyond 
the iron zone to any great distance. It also appears that there 
is a diminution of the deposit at a distance from the surface. 
