Written in 1898
In the topographical survey
of the United States, all that portion laying between the Rocky Mountains and
the Sierra Nevada, up into the southeastern portion of Washington, is known as
the Great Basin. This basin was once an extensive lake bottom, and
now, for the most part, filled with alkaline plains of the quaternary age. The
surface Is diversified by subordinate ranges of mountains, formed of tilted
paleozole rocks and extensive overflows of igneous eruptions. These ranges are
barren and shattered, and the stratafied rocks are often found in confusing and
chief characteristics of the Great Basin, alkaline deserts and subordinate north
and south ranges of mountains, are carried into Eastern Oregon, Washington and
Along the coast we find a prolongation of the Coast Range with its fertile
valleys of the cretaceous and tertiary. East of the Coast Range we have the
quarternary valleys, covered more or less thoroughly with immense outpourings of
igneous rocks. These extend into Idaho. On the north we have the characteristic
carboniferous rocks extending into Northern Montana interspersed with
quarternary and tertiary lake deposits.
mountains of Eastern Oregon present strong evidence as belonging to the Sierra
Northeastern portion of Oregon is formed by the prolongation of the igneous
plateaus of Washington, while the southeastern portion belongs to the Great
Basin which comes up from Nevada. It is traversed by the same block-tilted
ranges peculiar to the basin region farther south. The general surface is
covered by quaternary lake deposits, and outflows of igneous rocks. The basin
ranges of mountains are all of the block-tiling sort, and, where exposed show
paleozoic rocks of great thickness. In these ranges is where mining is almost
exclusively confined while between them lay great alkaline plains.
characteristic rocks are of the igneous type-granite, seyenite, diorite, gabbo,
and diabose in the holocrystallime varieties, and phorphyries, trachytes, and
basalts in the porphyritic sorts, with some pitchstone and obsidian. In Baker
County we find slates and granites predominating, although, for the most part,
covered by igneous overflows.
a producer of gold and silver, Oregon is taking a prominent place, and Baker
County is the seat of the chief mining districts of the state, and presents the
characteristic placers and quartz ledges of the Sierra Nevada region of
California, Grant and Union Counties are also important gold producing
Outside the counties forming Southeastern Oregon, the gold and silver production
is very limited. Some auriferous beach sands are encountered at Port Orford,
where the ocean has access to cliffs of gravel, which is broken down by the
waves. A sorting action occurs and the gold is accumulated and can be gathered
up at low tide. The quantity, however, is small, and the deposit is of interest
chiefly as to its scientific aspects. The placer mining of Eastern Oregon is of
considerable importance. Our placers have produced many millions and they are
extensively worked to-day.
Quartz mining is in its Infancy yet. Probably not more than 800 stamps, or their
equivalent, are cropping in Baker and Grant Counties. It is safe to conclude,
however, that this number will be doubled in the near future Whether our ores
are workable at the highest saving by the stamp mill will be subsequently
considered. Where we find the Great Basin tilted sort of mountain ranges we can
reasonably expect to find sufficiently rich quartz ledges to work into mines.
There are but few directions to be given that will aid the prospector in his
search for ore. The mere inspection of the outer surface of rock will give but a
feint idea as to what it contains, and this is preeminently true in our so
called rebellious ores. When a ledge is exposed the examination of the walls is
often as highly important as testing the ledge matter itself. From the earliest
times it has been maintained that the soil overlaping mineral veins is
peculiarly adapted to the growth of certain sorts of vegetation. While this is
not an infallible guide as to the location of a mineral vein, It is interesting
to note that many plants are eagerly looked for by many prospectors. For
instance, near Giesen, Germany, an iron vein is traceable for over two miles by
a growth of birch trees, while the surrounding country is thickly wooded with
oak and beech. Gum trees, and trees with dead tops, are found most numerous in
soil containing "float" galena in clay. The beech tree prefers a limestone soil,
and extensive limestone beds have been found by working out this hint. In
Montana prospectors look for silver where they find a speies of Erigonium
growing. This plant is closely related to our common dock, which it also closely
resembles, and to our sorrel and smart-weed. And lastly, all plants growing over
zinc deposits nave yellow flowers. Here is a great field for some energetic
student in which to create an -logy that deals with the influence of the soil
constituents on the selection and growth of plants.
is universally conceded that ledges formed as fillings of true fissures make our
largest and most permanent mines. Therefore the prospector should be able to
easily and surely distinguish a fissure vein. Other veins have been able to
produce very rice working ore, but the true fissure vein is a reasonably sure
indication of permanency and values. It has comparatively smooth, generally
striated surface, and frequently covered with a clayey or talcose selvage. This
selvage or "gouge," is supposed to be evidence of pressure and movement. Of
course the clay selvage is not always present unless the finely comminuted
material produced by the grinding of the faces has been subjected subsequently
to the action of the water, which carries off much of the soluble matter,
principally the alkaline constituents, leaving the argillaceous or talcose
residue. These striated walls and selvages are frequent concomitants of
ore-bearing fissures, but by no means absolutely essential. Both may be wanting,
and such occurrences are frequent. The ledges or rather ore bodies are of a very
eccentric nature, sometimes, as one familiar with Cripple Creek said, "The
tenderfoot is looking for gold where he finds it, while the old miner Is looking
for it where it ought to be," and the former were quite as successful as the
as to the ledge matter itself. It is quite beyond question, at the present day,
that by far the largest amount of gold ore deposits are those wherein the metal
exists in very finely divided particles disseminated more or less uniformly
through the vein matter, and it is perhaps safe to say that a very large
proportion of this exists in connection with the various sulphides and arsenides
of iron, copper, lead, zinc, antimony, and bismuth. The miner, as a rule,
classifies all these various minerals under the common term "sulphurets," which
term, by the way, means very little.
Whether the gold under these associations is chemically combined with the "sulphurets,"
or only held mechanically is very difficult to tell. It is the opinion of
metallurgists generally that the gold is perfectly free and mechanically
associated with the various minerals. It is very evident that where the gold so'
occurs it is in such all extremely finely divided condition that the term "flour
gold" is not inappropriately applied to it. The localities where the gold is
found 'free," or unassociated with the above mentioned minerals are
comparatively few, when much of the free milling ore contains more or less "sulphurets"
carrying a goodly proportion of the precious metal. There are also larger
districts where the gold found is entirely in connection with the sulphides and
arsenides of iron, copper, etc.
The most common
gangue matter of the gold-bearing ledges is quartz, with smaller amounts of
calcite, siderite, borite and occasionally some of the feldspars, pyroxine,
siderite, blend and related compounds. The origin of the metalic contents of
veins must be traced either to the igneous rocks of the district or to the
ocean. The precise method by which the entire vein matter was placed in the
fissure is one of dispute. The weight of opinion, however, is that it was by
means of hot alkaline solutions-hydroplutonically. Space wid not permit of a
complete discussion of the subject further.
employed for the extraction of the valuable part of the ores is termed
"ore-dressing." The ideal way would be as we crack a nut and extract the kernel
unbroken, while nothing is left in the shell. Any process of ore dressing that
approaches this is nearing perfection. This is done moth mechanically and
chemically to-day, and the precise process to employ in any given case is a
problem often difficult of successful solution.
In ancient Egypt
many years before the time of Christ, gold ore was crushed between heavy stones,
and the more or less finely comminuted material washed with a stream of water.
The gangue and much of the values were swept away, and any gold remaining
secured. Very early records also mention the addition of mercury to facilitate
the collection of the gold. To-day we use toe selfsame method, inn with about
the same results, as pre-historic man used. The only improvement for years past
has been toward development in rock crushing tilling to save values is only a
secondary matter. The average mill man bends his every effort toward crushing
rock and any remonstrance directed against their accepted but antedated methods
is looked upon as coming from one but a short way removed from an accredited
lunatic. He is conservatism run wild when it comes to the treatment of his ore,
but a most profligate liberal when it comes to saving his gold. When assays
showed $40 to $60, while the mill returns showed from $15 to $20, some bright
genius discovered the terms "refractory and "float gold," to explain why so much
eluded their grasp, and the amount of consolation afforded the average miner
during years past, by the use of these terms, has been Infinite. Many camps have
been entirely abandoned because, for instance, a stamp mill would not save
sufficient values to pay running expenses, and still assays showed exceptional
values; but the ore was "refractory," and refused to lie worked. The day has
come when a single operation. or any one "patent" process will suffice. The
stamp and manner Is not to be considered a universal specific fur gold
extraction. The only proof of the pudding is the eating.
But by far the must
blighting element to the advancement of scientific metallurgy is the "mining
expert." He has learned a few mining phases. He possesses the ability to put
them together fit connection with a few poorly made assays from more poorly
taken samples and deduce fabulous dividends from a ridiculously small
investment. Perhaps the source of the trouble is that any one is permitted to
attach those mysterious cabalistic letters, M. E., to his name. There are many
honest, conscientious men in the profession, but it is no easy task for the busy
business man to distinguish the genuine from the false.
There is another
class, who, though well-meaning, are no less a retarding force to the
advancement of scientific mining applied in a rational, business-like way. These
are the class called by a friend of mine, "kidgloved Frieburgers." They have
been just turned loose from some educational mining hot-bed. They confront the
miner with a lot of crude, unapplicable theories, and of course, failure
results. This only more firmly weds the miner to his own methods.
But to return to
ore dressing. In this I can but broadly hint at some of the things that
influence treatment, and which I trust will lean to a more careful study of the
conditions presented in each case. More attention paid to this in the beginning
of our equipment will reduce greatly the numbers of failures, and render many a
property a dividend produced instead of a financial loss. Perhaps the first
great question to settle is what elements are found in the ore, if any, that
will influence treatment. The ordinary classification of ore into "tree milling"
and "refractory" is hardly sufficient. The hitter term is of a too indefinite
meaning. The following schedule embraces the present methods of dealing with
1st. If free gold, with no "sulphurets,"
free gold milling.
2rd. If some free gold with
"sulphurets," free gold milling, with fine concentration and chlorination or
smelting of the product.
3rd. Heavy iron pyrites,
carrying gold, fine concentration and chlorination or smelting of product.
4th. Chloride of silver
ores, free milling.
5th. If silver ores with
base metal "Sulphurits," fine concentration and smelting of product.
6th. Heavy mineralized ores
of lead, copper, tin or zinc, Course concentration and smelting.
7th. Light mineralized ores
of copper, lead or zinc, tine concentration and smelting.
8th. Copper pyrites or
chalcapyrite, coarse or full concentration, with partial roasting and melting.
In treating ores by course
or title concentration, there are certain minerals, of no value in themselves,
that must be taken into very careful consideration.
1st. The partially
decomposed ores are very difficult to concentrate, especially if they are easily
2nd. It is very difficult to
separate iron pyrites, copper pyrites, mispickel, or sulphate of barium, from
3rd. The rocks chlorite and
epidate are very difficultly removed from copper ores.
4th. Lead and antimony,
especially in the form of sulphides, are very injurious to the amalgamation of
either god or silver.
5th. Talic is injurious to
6th. Copper pyrites,
chalcapyrite, sulphate of copper. and all soluble acid salts to treatment by
The practice of free milling
is familiar to all who are conversant with the present stamp milling practice.
There are many things to consider in this method at treatment where various ores
are subjected to it, and the losses are sometimes very heavy, but the limits of
this article are too small to consider them further. When, however, our ore
contains valuable "surphurets, or is familiarly known as refractory, the
question of the economic treatment of them is then one of the most complex that
mining and metallurgy has to consider, and the one who would solve it must put
favorite methods religiously away. The conditions of mine and ore are to be the
chief elements in the solution. The process must be adapted to the ore, and no
attempt made to adapt the ore to any prejudiced process. The question of
crushing must receive must careful attention. It is not rock crushing that is
wanted by scientific milling. After the rock has been properly reduced the
subsequent treatment would appear simple, but in fact, it is peculiar to itself.
Concentrators that work well on one ore may not on another. Each system must, be
peculiar to itself.
After the concentrates have been produce, their subsequent treatment would
appear simple, but, in fact, it is often most difficult. If they are to the
smelted the question is perhaps quickly adjusted, but if they are to be treated
by chlorine, they must be at least partially roasted. The process of roasting
pyrites in order to effect the extraction of the highest percentage of values is
not -so simple as many suppose. Pyritic roasting is almost as old as gold
mining, and its importance is increasing each year. True, there are many
processes suggested for the extraction of the gold and silver from pyretic ores
without roasting, but their success is limited to peculiarly consituted ore.
There is no subject connected with gold mining which demands more careful
consideration than the economic treatment of our pyritic ores. The driving off
of the sulphur and arsenic by the application of heat, is, no doubt, very easily
accomplished, but very fee ores are so simple as to contain but the sulphides
and arsenides of iron. Subsequent treatment will determine how thoroughly the
roasting process must be done, if the roasted ore is to be amalgamated. The
roasting must be absolutely dead, for partially rousted ore is worse than no
roasting at all.
Many ores have a tendency to agglutinate on roasting. To obviate this evil sand
or charcoal are added, but the addition of charcoal to ore containing lend or
antimony is very detrimental.
detailed consideration of tile various "processes" for the treatment of our
"refractory" ores would occupy more space than is allotted to me. Mining in all
its departments is a most legitimate form of manufacturing, and when properly
conducted furbishes the safest investments for capital. It is like any other
form of manufacturing, subject to the law of diminishing returns, and each
special process must be adapted to the conditions.
Eastern Oregon Gold Fields
Mining in Oregon
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