302 The American Geologist. November, i898 
been confirmed by Pumpelly in a masterly research into the 
metasomatic generation of various minerals of the copper- 
bearing rocks.* Hunt makes nnich of this fact, and expands 
it into such scope that he deduces the general law that the 
alkaline silicates are naturally one of the products of the cre- 
nitic process, and inferentially that the orthoclase of the veins 
and amygdaloids is a product of alteration of the diabase 
which contains them. This, however, is wholly a gratuitous 
and even impossible inference, not only because of the difficul- 
ties already referred to, but because of the attendant state- 
ments of Pumpelly. It will be seen, by an examination of the 
tabular grouping of the secondary minerals of the copper- 
l^earing rocks presented by Pumpelly, that these minerals ap- 
peared in a certain order, as they are often super-posed in 
geodes and veins upon each other, and that orthoclase appears 
near the end of the series. In this table there are thirteen 
steps of mineral genesis, metallic copper being number six 
in the series and orthoclase number twelve. It seems, there- 
fore, that not only did the zeolitic minerals all precede the 
formation of orthoclase, but also that metallic copper was 
earlier than orthoclase. The significance of the occurrence 
of orthoclase in cavities in the diabase, so far as that fact berrs 
on the source of its elements, is less than that of the occur- 
rence of copper, but if, for the sake of the argument, it be 
considered equal to that of the occurrence of copper, we are 
confronted, on the argument of Hunt, not only with the deri- 
vation of potassium from diabase, but also with the generation 
of metallic copper in large amounts ^ from the same rock, 
neither of which elements exist in diabase in its normal and 
pure state. 
We are, however, relieved of this difficulty by a different 
explanation. The origin of metallic copper in the Keweena- 
wan rocks is now generally attributed to the circulation of 
mineral waters carrying the salts of copper in solution at a 
date considerably later than the origin of the diabase, such wa- 
ters having parted with their copper occasionally in cavities 
in the diabase, but most abundantly in the cavities in the 
interbedded conglomerates \ 
*Am. Jour. Sci., Vol. II, Sep., Oct., Nov., 1871. Proc. Am. Acad. 
Arts & Sci:, XIII, p. 253, 1878. 
tPumpelly, Am. Jour. Sci., Vol. II., 3rd Sen, p. 352, 1871. 
