ORE DEPOSIT THEORIES. OV 
metals of these deposits, namely, iron, copper, silver, and 
gold, are not specially characteristic of either acid or basic 
rocks, but occur in both. This we know partly from the 
results of analyses, which have been made with the object 
of determining the minute metallic contents of rocks, and 
partly by the presence of these metals both in tin veins 
which have derived their metallic contents from granite, 
and from apatite veins which have derived their metallic 
contents from gabbro. 
2. In some cases the deposits have, as stated above, been 
proved to have been formed before the final consolidation 
of the eruptive mass, with which they appear to have a 
genetic connection. : 
3. In some cases the deposits are accompanied by minerals 
containing fluorine and boron, as, for example, fluorite, 
chondrodite, muscovite, tourmaline, and axinite. In many 
> cases, however, these minerals are either absent or are 
present only in small quantities. In some cases, on the 
other hand, they occur in large quantities. 
4. In some cases pyritic deposits contain such minerals as 
garnet, epidote, &c., wnich are well known as contact meta- 
morphic minerals. They also often contain small quantities 
of magnetite and specularite, and sometimes these minerals 
are present in considerable quantities. This seems to point 
to the possibility of a connection being established between 
these deposits and contact metamorphic deposits. With the 
significant exceptions uf tin veins and apatite veins, the 
association of primary sulphide and oxide ores is almost 
unknown in fissure veins. 
5. The suggested sedimentary origin of these pyritic 
deposits has been definitely shown to be impossible in a 
great many instances, from the fact that many of them are 
not conformable, or not strictly conformable, with the 
strata. There is no more difficulty in explaining the general 
approximate conformability of pyritic deposits than there is 
in explaining the general approximate conformability of 
_ contact metamorphic deposits. Vogt shows that out of 87 
separate contact metamorphic deposits examined by him in 
the Christiania district, no less than 80 were conformable 
with the strata. As these deposits are certainly not of 
sedimentary origin, it is evident that the conformability of 
ore deposits may have another cause, and the conclusion is — 
not unreasonable that in the case of these two classes of 
deposits, which are both intimately connected with eruptive 
rocks, the cause of their conformability is the same. 
Supposing, for argument’s sake, that both of these classes 
of deposits have been formed during or soon after the 
