166 
AMERICAN GEOLOGY. 
with quartz, as usual, but the most productive locations are the 
deposit or branch mines. The indications bear a favorable 
aspect in the Canadian mines. From North Carolina, the gold 
belt extends south through South Carolina and Georgia, disap¬ 
pearing at last beneath the tertiary of the Atlantic slope. 
OF THE PYRITES AND AURIFEROUS COPPER LODES OF THE 
ATLANTIC SLOPE. 
§ 102. There are classes of gold mines in which copper is 
rarely if ever found. There is first the disseminated gold of 
the soft slates. When the metal is widely diffused in the rock, 
the produce amounts to from ten to thirty-five cents per bushel 
of ore. These masses of slate may yield gold through a width 
of one hundred feet; some places are richer than others. They 
may be called mass mines. Tn auriferous rocks of this kind, 
the gold is combined with very small particles of sulphuret of 
iron, which are decomposed for thirty or forty feet in depth, 
but below the water level, the sulphuret becomes visible. Cop¬ 
per is never found in this species of auriferous deposit. It is 
absent again in the thin auriferous belts, which rarely exceed 
six inches in width, in slates of a similar character. These 
are false veins, as they are destitute of walls. So copper is 
absent in some of the veins of auriferous iron pyrites. But a 
very large proportion of the veins which carry gold carry cop¬ 
per also; and some of them have become the best copper mines 
in North Carolina. The upper part, or back, as this part is 
sometimes called, is simply a decomposed iron pyrites; but 
when the lode is penetrated thirty or forty feet, the triple 
compound of sulphur, copper and iron, comes in, and increases 
in quantity with the descent, or in other words, it becomes a 
copper lode. A few years ago a change of this kind was 
dreaded, as it was invariably deemed necessary to abandon 
them, for no other reason than that it cost too much to separate 
the gold from alloy, which would be found with the copper. 
At this time many of these abandoned gold mines are regarded 
