Ta RNA ag he

366 V. DOLMAGE.

tite, and a difficult one to explain, is that of following the gangue
contacts very regularly, but inside the chalcocite areas, and sep-
arated from the contact by a narrow border. Aggregates of it
do not occur excepting near the epidote and calcite. It would
appear from this that the hematite came in at the same time as
the epidote, and some time after the formation of the quartz-
sulphide vein.

No magnetite was seen in the ore excepting a few scattered
erains near the margins of the veins.

Of the gangue minerals, quartz is the most important. It is
unusually full of inclusions of transparent and opaque minerals.
Some of them are undoubtedly hematite blades, but these are not
sufficiently plentiful to color the quartz, and must, therefore,
form a very minor portion of the inclusions. Many of the in-
clusions are filled with liquid, and contain movable bubbles. The
inclusions are arranged in lines which are roughly parallel, but
are not straight, and conform to no apparent system.

Epidote is next in importance among the gangue minerals. It
forms a band an inch, or more in thickness, on the east wall of
the vein which is yellowish-green color, and has a sugary tex-
ture. From this band numerous veinlets branch off irregularly
into the ore. It is occasionally seen in euhedral crystals in the
calcite, and is of an earlier period than the calcite.

Calcite occurs as irregular masses in the ore several inches, or
more, in size, and also as veinlets cutting the quartz. It contains
only blue chalcocite, the silver minerals, and copper carbonates,
all of which replace it along cleavage lines.

Laumontite was found rather plentifully along the margins of
the vein; it has a light pink color, and soon crumbled away when
exposed to the air. It was seen in one of the thin sections and de-
termined by its optical properties.

Alteration of the Country Rock.—The tuffs adjoining the
vein are surprisingly little altered. The color is changed from a
red toa slaty green, and chlorite, epidote, quartz and occasionally
a little laumontite along the walls have been introduced. The
alteration does not extend more than a few inches from the vein.
Adjoining the dikes the alteration is more intense, and consid-