CHANGES WHICH A VEIN UNDERGOES. 
137 
The veinstone in which gold, silver, lead, copper and zinc are 
found, in this country, is generally quartz, or in the language 
of miners, flint; and we have numerous examples of rich and 
poor veins in this kind of gangue. I know of but one lead 
vein in North Carolina which has a calcareous gangue. The 
following kinds of mineral form the veinstone of sundry mines 
in this country: Quartz, calcspar, pyroxene, hornblende, feld¬ 
spar, phosphate of lime intermixed with a small quantity of 
hornblende, prhenite, and magnesian carbonate of lime. Either 
of these minerals may form good stoping ground, or either of 
them excepting the calcareous may be bad or hard. Much 
depends upon the connection of the gangue with the wall; if 
this is such that a gad or pick can be employed in taking down 
the vein, it belongs to the kind called easy or good ground. 
Quartz sometimes partakes of the mineral character of a horn- 
stone; it is then an exceeding tough rock; it is an expensive 
vein to take down, and though it may be rich, yet the expense 
attending its working is so great as to consume the expected 
profits. 
CHANGES WHICH A VEIN UNDERGOES NEAR THE SURFACE. 
§ 90. Every miner has observed that the part of a vein near 
the surface, differs from that below. The change takes place 
at that depth where water always remains. The difference 
between the part of a vein near the surface and that below 
water, consists in two particulars. There is first a mechanical 
difference in these two parts of the vein. The veinstone is 
porous, and the metals are oxides, in loose, slightly coherent 
masses. I have in mind the gold veins of the south. In the 
second place, below water, the veinstone is more solid, and the 
metals are sulphurets, disseminated in the gangue. The upper 
part is brown, or reddish brown, and the quartz is thus 
stained; while below, the gangue is blended with specs 
of metal, or perhaps with the elongated masses. This change 
in the character of a vein is due to the action of the 
atmosphere, aided by the alternations of dry and wet states to 
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