, 1900-02-20

may Ne Wlue or narrow, and may nav
sharply defined walls on either sid,
or merge gradually into the surround
ing country rock. There are two kind!
of veins-tirst, veins proper and sec
ond, dikes. Veins proper are supposed
TO have been originally clefts or ifs,
sures in the rock which have been fill
ed with their mineral contents, by dep,
Osition from watery solution. The the.
Dry in brief is that water penetrates
to great depths through cracks and ifs,
sures and pores of the rocks, and III
doing this becomes greatly heated and
charged with substances that have the
power to dissolve metals contained in
minute quantities in the rocks through
which it passes. The water carrying
these dissolved metals reaches some
fissure through which it can again rise
to the surface. In doing this it OF
course loses heat in contact with the
colder rocks, and pressure in getting
near the surface and thus losing its
power to hold the metals in solution
it deposits them on the sides of the
assure or cavity. The presence of de-
caying vegetation or organic matter in
general will aid in depositing the met
ais in various forms in the assure.
bikes are sheets of igneous rock,
such as porphyry, diorites which have
come from below and filled a crack or
assure in the rocks. They are some
times mineralized and carry values in
metals. When a dixie is mineralized
the metals in it have in all probability
been brought from depths at the time
the assure was being filled.
Sometimes there are layers or beds
of rock not strictly veins or dikes,
which carry mineral values, the metals
being placed there by one of the above
described means. Thus we may have
sheets Of granite or porphyry that are
valuable in mineral. The values may
be uniformly distributed or what is
more common may occur in zones or
layers which gradually fade out into
loNh. lHlS occurrence III
zones" or "chutes" is also character
istic of veins. 1t is rare that a vein
carries mineral values all through it,
but the values occur concentrated To-
caily along certain lines. The chutes
may dip at any angle within the vein.
"A vein proper consists of the miner
al or ore and the gangue or vein fill
ing. The filling is often quartz, cal
cite or Gale spar, fluorite or flour spar,
usually found as purple or greenish
cubes, barites, or heavy spar, and 9TH
ers less common. Quartz is by far the
most common. The minerals in which
the gold and silver is found are pyrite
or iron sulphide, chalcocite or sui
phides of copper, ~chalcopyrite and Dor
mite or sulphide of iron and copper.
galena OF sulphide of lead, sphalerite
or sulphide of zinc, known also as
black jack and others less
The gold and silver is present in these
minerals in small quantity, usually in
the form of some special mineral OF
gold or silver which is included in the
greater mass of the minerals named.
Sometimes the gold and silver miner
ais are alone present or are in sufficient
quantity to be seen by the eye, as for
instance where the ruby silver min
erals OF the tellurides of gold and sill
yer are found. But in most cases the
common minerals named carry the
values. Iron and copper sulphides are
apt to carry gold and zinc and lead
though any of them may carry both.
Thus it is seen that while we may
have a gold or silver ore, We may at
the same time have a copper; lead or
zinc ore, If these last named be pres
ent in sufficient quantity.
Gold and silver occur in the native
or pure state, especially gold. When
found in this way it is usually as free
gold in quartz lodes or veins.
The term of oxydized and
died, base or refractory ores, is COM
hhoh's uoSu. ohsulLtu oltS dle luOSt
found above the permanent water lev
ell of the ground and base or refractory
ores below the water level. The line
of water level may vary crafty and
depends on the district, amount of
rainfall, level of the main drainage by
streams, etc. In very dry countries
the ores may be non-oxydized even
above the water level, as in our own
districts in the vicinity.
The reason for this change in the
ores Is that the air and percolating
waters of the surface carry oxygen to
the sulphide ores, which in the
purse Of time acts on the sulphur
and eliminates it, changing for in
stance, the sulphide Of iron into the
common iron rust or iron stain and
the copper sulphides into the green
and blue carbonates of copper, ma
lachite and azurite or the red oxides,
the lead sulphide into lead carbonate,
etc. In the transition some metals,
such as copper, pass into a soluble
form and then are carried into the
ground by the water level and there
perhaps ~redeposited. This is the rea-
son that while there may be little cop
per showing at the surface it may be
present In greater quantity at the wat
er level and below. OF course IL the
surface shows much sulphide Of copper
and little Of the changed ore. this ac-