156 
AMERICAN GEOLOGY. 
gold of this country was confined to talcose slate. This is now 
known to be untrue; for, in addition to talcose slate, it is found 
in mica slate, hornblende, granite, and limestone. It has a 
wide range of relations, and it would seem that the metals have 
geographical rather than geological boundaries; that is, in a 
given district all the rocks may be expected to contain them; 
or, in other words, that there are certain types of association 
which belong to certain geographical districts, and that in 
order to pursue successfully mining interests, we must study 
that type. The doctrine, however, holds good, that a certain 
rock is commonly the bearer of a given metal rather than any 
other. 
In this country quartz is the common associate of gold. But 
other associates may exist: the massive talcose slate, horn- 
blendic gneiss, hornblende, granite, mica slate, limestone, and 
even serpentine. In talcose slate, gold may be disseminated 
in the rock for from forty to sixty feet in width. It is a mass 
of rock, or a mass mine, which bears no semblance to a vein, 
except that belts or strips of it are richer than others; but it is 
impossible to detect walls or defined boundaries to the aurifer¬ 
ous parts. The gold of the mass is mechanically mixed with 
particles of a brown substance, disseminated in the rock suffi¬ 
ciently abundant to impart red and brown tints to the mass. 
These are sometimes of a rosy or peach-blossom color, indicat¬ 
ing the presence both of iron and manganese. There is no 
doubt that these brown and reddish particles were sulphuret of 
iron which held the gold in mechanical combination. Where 
the auriferous mass is inspected, it is found to consist of fine 
grains of quartz, which are only slightly coherent, intermixed 
with silvery talc, which at the first inspection seems to pre¬ 
dominate, but on closer observation proves the predominance of 
quartz in its composition. This kind of rock might with pro¬ 
priety be called talcite. 
Gold is also disseminated through a pure saccharoidal quartz, 
which contains neither sulphuret of iron or talc; but this white 
and pure quartz may be contained in a vein or mass subordi- 
