: NORTH-WESTERN DISTRICT (No. 1). 61

latter part of the season. The west-bank trail up American creek is, however, a better route
and was put in good shape with assistance from the Department of Mines. The lower camp
is on a ridge in the yvalley-bottom at altitude 1,700 feet. The upper camp at the workings is at
altitude 2,415 feet. The general formation of the area is the Bear River formation of frag-
mentals and lavas with some argillite, intruded by numerous dykes of feldspar porphyry, augite
porphyrite, and lamprophyre. ‘The structure of the area is featured by zones of intense shearing
and numerous faults. In places the intensity of these factors approaches a regional condition
and gives the impression that where control is lacking a dispersal of mineralization accompanied
by spasmodic and lenticular development of ore-shoots may occur.

The main showings on the property consist of two wide and erratically defined replacement
zones. The filling of these zones consists mainly of an intergrowth of quartz and jasper with
some barite. The Mann yein, 16 to 20 feet wide, strikes about N. 40° BE. (mag.) and dips about
45° south. It has been traced for several hundred feet up the rugged talus-covered mountain-
slope from altitude 2.485 feet, spreading or swelling finally in a rugged gully at about altitude
2,600 feet, and terminating. This zone is generally spasmodically and sparsely mineralized with
chiefly zinc-blende and some galena in places.

The Highgrade yein outcrops at about 3.000 feet altitude in a somewhat inaccessible, broken-
up, and dangerous canyon area. It is 6 to 8 feet in width, strikes N. 40° W. (mag.), and dips
30° west into the hill. The vein is composed of a quartz-jasper-barite gangue with generally
sparse mineralization. A streak of 8 to 18 inches in width, favouring generally the foot-wall,
contains some small high-grade kidneys and yeinlets of zine-blende, galena, argentite, and a
mineral thought to be stromeyerite, spasmodically distributed over a length of about 100 feet.
It is understood that this vein has been traced for an appreciable distance. Other showings are
reported to exist on the property, but were not examined.

During 1929 operations have been concentrated on exploration of the Mann vein in the Mann
tunnel at altitude 2.440 feet; and of the Highgrade vein by a crosscut to the vein and a drift
along it, at about 3,000 feet altitude, in the hope of intersecting the extension at depth of the
ore-showings on the surface.

At the time of examination the Mann tunnel was advanced to about 200 feet along the
foot-wall of the vein, with two crosscuts of about 35 feet at intervals to the hanging-wall.
Fair, though patchy, mineralization of chiefly zine-blende shows for a width of about 5 feet
along the foot-wall from the portal to about 40 feet in. From there to the face, although
the vein shows widths of over 20 feet, mineralization is very irregular and generally sparse.
A sample across 5 feet of the foot-wall at the portal of the tunnel assayed: Gold, 0.02 02. to
the ton: silver, 10 oz. to the ton; lead, 2 per cent.; zine, 11 per eent. This foot-wall shoot
continues with lenticular irregularity for about 40 feet along the tunnel to the winze. It seems
to be best developed along the cross-fractures.

From the westerly swing of the tunnel to the slip mineralization appears to be very irregular,
with an occasional small patch of fair-grade zine ore. The structure of the vein is noted to be
banded and brecciated, with angular fragments of andesite in the vein-matter. The best develop-
ment of ore is in the banded sections. A sample along the north wall of the second east crosscut,
representing the first 15 feet from the drift, assayed: Gold, trace; silver, 8 oz. to the ton; lead,
trace; zine, 12 per cent. A sample along the last 13 feet of the north wall of this crosscut to
the face assayed: Gold, trace; silver, 1 0z. to the ton; lead, nil; zine, nil. A sample of the
selected mineralization exposed in this tunnel assayed: Gold, 0.08 oz. to the ton; silver, 1.2 oz.
to the ton; lead, 1.3 per cent.; zinc, 22 per cent. Should this vein, after intensive exploration,
show a consolidation of ore-shoots, it may be possible that mill-grade tonnage of zine ore could
be developed.

In this development-work a marked irregularity of the walls, particularly the hanging-wall,
features the vein. This is accompanied by a swelling and diminution in width, attended by
irregularity of strike and dip in comparatively short distances. This is apt to sometimes give
the appearance of faulting or dragging. Much faulting is assumed to have affected this deposit,
put in this type of vein occurrence such conclusions should not be hastily formed. At 30 feet
from the face the vein swings about 10° S. along a fracture-plane striking S. 20° W. and dipping
g0° east. The tunnel continues on in the foot-wall rock and at the face would be about 25 feet
west of the foot-wall of the vein.

At about altitude 3,000 feet development on the Highgrade vein was carried on from a
erosscut tunnel and a drift along it for about 30 feet from the point of intersection by the

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