VEDOEMAGE.

354

small blebs, often situated at the points of the irregular grains of
chaleopyrite. Ihe tetrahedrite occurs im only mucroscopic
amounts, and is seen as small rounded areas in the galena with
smooth contacts which indicate a probable simultaneous depo-
sition.

All the minerals are cut by small veinlets of limonite, along
some of which were seen a little covellite. The smooth contacts
of some of these veins undoubtedly indicate replacement, but
others have sharp, angular contacts which show that they occupy
cracks formed by crushing of the ore. Malachite and azurite
are present in small amounts.

The alteration of the country rock is intense. The tuffs are
changed to a light green, fine-grained rock somewhat like pro-
pylite, containing visible grains of quartz and pyrite. Under the
microscope it is seen to consist almost entirely of about equal
amounts of chlorite and sericite with a little epidote in a fine-
grained mass of quartz. In this groundmass are enclosed cor-
roded crystals of quartz which are probably primary, and have
been partly replaced by sericite and chlorite. Later than all these
minerals are numerous small veins of quartz. The granodiorite
is altered to sericite, quartz and chlorite, and slightly impreg-
nated with pyrite.

The order in which the minerals were deposited, as indicated
by the veining of the earlier by the later minerals, is as follows: |

Epidote,
Sericite,
Chlorite,
Quartz.

IT.{ Quartz (gangue).

eayiielee:

Zinc blende,
Chalcopyrite,
Galena,
Tetrahedrite,
Argentite.

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