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COPGER SLL ZER VEINS-OF TELKWA DISTRICT. 369

important to shake the theory that the primary ore of this claim
also came from solutions emanating from the granitic stock.

According to this theory, it matters not whether the chalco-
cite be considered as primary, or as secondary after bornite, and
that the hematite followed the bornite-gangue contacts instead
of the chalcocite-gangue contacts, but for reasons that will be
given in a later paragraph the chalcocite is believed to be primary.

Primary Chalcocite—One of the most disputed points in the
current literature on economic geology, and at the same time a
most critical point, is the question whether or not chalcocite is
ever a primary mineral. It is conceded by all that it is a most
common secondary product, and while a few believe that it may,
in rare cases, be primary yet there are many who maintain that
no case of the primary origin has yet been proven. It 1s, there-
fore, with some timidity that I claim for this chalcocite a primary
origin, though the evidence seems to point strongly in that direc-
Ol tne inportance Ol “the Matter rests on the question,
whether the mineral can be taken as a positive criterion for prov-
ing the ore in which it is found to have been enriched by descend-
ing meteoric waters.

Some of the strongest evidence against the enrichment theory
for this ore comes from the relations observed in the Excelsior
claim. The microscopic structures show fairly certainly that
some of the bornite of the graphic structures is of later date than
some of the chalcocite. Areas of chalcocite surrounded by nar-
row persistent rims of bornite which send sharp wedge-shaped
spikes into the chalcocite cannot be explained in any other way,
and such were seen in several cases. The bornite rims are often
connected with the bornite of the graphic structure, as for ex-
ample, in Plate XXIII., d. This being the case, then, if the chal-
cocite is secondary, the bornite must also be considered secondary.
But there is no evidence to substantiate this, the bornite is often
closely associated with the chalcopyrite, but there is no sign of
veining or replacement along the gangue contacts, or indeed any
structural evidence of secondary replacement. On the contrary
their smooth, rounded contacts, and mutual intergrowths indi-
cate a contemporaneous and a primary origin for both. The

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