This mine is located a short distance from the town of Julian, and is
equipped with a steam hoist and mill combined under one roof. The new
shaft, which was started nearly three years ago, was sunk on the vein
for 50 feet, at an angle of 75°, at which depth the shaft left the
crevice and continued vertically to a depth of 225 feet. From this point
a crosscut was started back toward the vein, running at an angle with
its strike, the idea being to reach a pay shoot as quickly as possible.
The shoot in question was the south extension of that developed in the
old workings. The vein was encountered, and the drift continued along
its course. At about 30 feet from the point of intersecting the vein in
this drift of the shoot was found. It was hard, blue, rather
glassy-looking quartz, filled with minute black particles, and showing
considerable gold, some of the rock being very high grade.
The drift was continued along the vein, and finally reached a point over
the level that had been run south from the old shaft, which is 300 feet
deep. This new drift was found to be 14 feet higher than the old level.
The mine was completely drained at the time of my visit, and a free
circulation of pure air was found throughout the workings. The ground
was ready for stoping, but owing to some legal difficulties arising the
property was lying idle.
The appended sketch will give an idea of the present development of the
Helvetia, which is one of the most promising properties in the district,
and a type of the best class of mines of its kind found there.
The Helvetia, like other mines of the district, occurs in the
crystalline schists, the quartz being found as lenses inclosed in the
country rock. Some of the lenses might be mistaken for fissures, but I
failed to see one possessing the characteristics of a “fissure.”
Nearly all the lenses exhibit a tendency to “make” into the hanging wall
side of the country rock, the lenses of quartz following each other in a
general direction, but at an angle with the stratification of the
schists, and are separate and distinct from each other, being separated
at the ends (where they sometimes overlap) by the “leaves,” as they may
be termed, of the schistose country rock. These lenses were doubtless
caused by a compressive stress on the schists, which had a tendency to
split them, but was not powerful enough to cause an abrupt fracture. The
accompanying sketch may convey an idea of the occurrence of these quartz
lenses.
[Illustration: _WORKINGS OF THE HELVETIA MINE NEAR JULIAN_]
[Illustration: _LENTICULAR QUARTZ BODIES IN SCHISTOSE ROCK_]
By the above sketch it will be observed that there is a tendency on the
part of the quartz lenses to follow a given direction, which lies at a
small angle across the strike of the schists, and that these lenses are
not connected, but occur independently, though all are the result of the
same force which flexed and split the strata.
Other mines about Julian were idle at the time of my visit, the most of
them being inaccessible, owing to water in the workings. Considerable
money has been expended on the Owens Mine in an attempt to drain and
recover the workings, but it was abandoned after several months of work
and considerable expense.
More activity was exhibited in the mines about Banner than any other
part of the district.