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Placer gold (pronounced: pla-sər),
can be defined as free gold that has eroded away from its
original lode, and has been deposited elsewhere by the
forces of nature. The size of placer gold varies from
microscopic dust up to large nuggets weighing several
hundred ounces.
Although the type of equipment used to mine placer gold has
changed over the years, the basic principal has not. The
most popular methods currently in use by recreational
prospectors are the gold pan, sluice box, metal detector,
dry-washer, dredge and high-banker; all of which have their
strengths and weaknesses. Some methods that work well in a
stream type environment will be of little use in the dry
deserts of the southwest, and vice-versa. The type of
equipment you choose will be dependent upon the conditions
in the area you are working, the size of the gold particles,
and your budget. If you are a new prospector, or thinking of
becoming involved with gold prospecting, take a moment to
familiarize yourself with the information listed below. It
is meant to provide you with a better understanding of how
each piece of equipment works and in what environments they
are most likely to prove effective.
Gold
Pan
The
gold pan is among the oldest methods in existence for
recovering placer gold. The first pans were made of woven
baskets or wood, then metal, and more recently, from
plastic. Pans are essentially a shallow bowl with riffles
built into one side. Gold-bearing materials like sand and
gravel are placed inside, and then the entire pan is
submerged in water. Once covered in water, the pan is
vigorously shaken which allows the heavier materials to sink
to the bottom. The pan is then tilted at an angle and water
is allowed to move in and out of the pan sweeping away the
lighter material. The heavier materials are trapped behind
the riffles and remain inside. This process is repeated
until all that is left behind is a streak of black sand and
hopefully gold.
Most
modern plastic pans cost less than $10; they are small,
light weight, and can be used anywhere that has water. The
only downside is that panning is a relatively slow process.
Unless a person is very experienced, the cubic feet of
gravel processed in a single day is generally small.
However, even if you don’t plan on using a gold pan as your
primary method of recovery, every prospector should own one
as they are ideal for sampling new ground.
Sluice Box
A
sluice box is a trough-like device that is fitted with
riffles along its bottom edge. Most sluices available today
are made of either metal (usually aluminum) or plastic. A
sluice, when properly set up, can process anywhere from 10
to 200 times more material than a gold pan.
A
sluice is used by slightly submerging it in a swiftly
flowing stream or creek, with the box placed in such a way
that the water is directed through it. Gold-bearing material
is then slowly shoveled into the sluice. The riffles in a
sluice mimic the natural bedrock cracks in a stream allowing
it to capture and retain heavy materials which pass through
it. The lighter materials will be washed away, but any gold
will drop behind the riffles and remain there.
The
sluice has several distinct advantages that make it one of
the more popular methods for recovering placer gold. These
include: low weight, portability, affordable (most cost
under $200), excellent recovery when properly set up, and
easy to operate. The only downside is that a sluice requires
a steady flow of running water to work properly. Desert
prospectors are more likely to employ other methods; however
persons living in an area with gold-bearing creeks, streams
or rivers, will certainly find the sluice box an excellent
choice.
Metal
Detector
As
its’ name implies, a metal detector is a device used to
locate metallic objects. Some are used for working
underwater, others for seeking out coins and relics, others
for hunting gold. If you are going to be primarily looking
for gold you should invest in a machine designed
specifically for nugget hunting. These machines are able to
handle high levels of ground mineralization and are designed
to be extremely sensitive towards tiny metallic targets. The
most popular types in use today are the VLF (Very Low
Frequency) and PI (Pulse Induction). VLFs achieve excellent
sensitivity and are preferred for chasing small, shallowly
buried gold. They do, however, struggle in areas of severe
ground mineralization. PIs are considerably more expensive
than VLFs, but they provide more depth penetration and will
outperform any other type of detector in mineralized or
“noisy” ground where gold nuggets like to hide.
In my opinion, the metal detector is the most versatile of
all the methods. It can be used virtually anywhere under any
conditions. Metal detectors can recover gold from hard to
reach areas where packing in other types of equipment is
extremely difficult. One downside is that they will not
recover fine gold. Metal detectors are most effective on
pieces of gold at least several grains in weight. Therefore,
if the area you are prospecting carries mostly fine or
“flour” gold, a metal detector will be of little use.
Dry-Washer
By far
the most popular piece of equipment used in the recovery of
desert gold was, and still is, the dry-washer. In its
simplest form a dry-washer consists of a metal screen (or
grizzly) supported by a frame that is fitted with an
adjustable riffle tray. Hand cranked models typically use a
system of bellows to move or vibrate the material across the
riffles, while blower-motor powered models are equipped with
a fan offset by a spinning counter weight. Air is pushed
through a hose by the blower which then causes the unequally
weighted fan to spin, effectively shaking the riffle tray.
As
dirt is shoveled into a dry-washer, the larger overburden is
immediately screened off while the smaller material passes
through and enters the riffle tray. The lighter materials
that enter the riffle tray will be expelled, while the
heavier materials are trapped behind the riffles. This
process leaves two distinct piles, which are known as the
coarse and fine. The coarse pile forms at the front of the
dry-washer; this is where the larger rocks that wouldn’t fit
through the screen will be located. The fine pile consists
of material that has been processed and will be produced
towards the back of the dry-washer.
Aside
from the metal detector, the dry-washer is the most
effective method for recovering gold from a dry-placer
environment. They are portable, easy to operate, and usually
only cost a few hundred dollars. Drawbacks include the
amount of noise and dust they produce, plus if the material
being processed is not completely dry, gold recovery will
suffer. I recommended that a metal detector always be used
in conjunction with a dry-washer to ensure that no large
nuggets are accidentally screened off and lost amongst the
coarse tailings. Persons living or prospecting in arid
regions will want to strongly consider adding a dry-washer
to their arsenal of equipment.
Dredge
A
dredge is a device used to suction up gold-bearing gravels
from a creek or river. It is essentially a glorified vacuum
cleaner consisting of a sluice box, nozzle, hose, water pump
and a gasoline-powered engine. The sluice box may be floated
upon a set of pontoons or set alongside the bank. Dredges
are very effective in the amount of gold they will recover;
however they require an ample supply of
water.
Dredging can be loosely classified as either deep water or
surface. Deep-water dredgers are usually experienced divers,
as they often dive to depths exceeding 20 feet. On the other
hand, surface dredgers rarely exceed 4-5 feet in depth, so
diving knowledge is not a necessity. They need little
equipment other than their dredge, a few tools and perhaps a
mask. The type of dredging you do will be determined by the
conditions in your area and the amount of money you are
willing to invest in equipment.
Dredges are usually classified according to the diameter of
the hose attached to it. While large dredges (6’+) are
capable of shifting more gravel, they are expensive, bulky,
and require a considerable amount of water. Small dredges
(4” and less) cannot match the capacity of their bigger
siblings, but in areas where the bedrock is shallow and
running water is scarce, a small dredge may actually
outperform a larger unit.
Dredges are very efficient; being able to recover gold of
all sizes, including nuggets, fine gold and dust. They are
capable of processing large amounts of auriferous material
and are the best means of working gold in a stream type
environment. As mentioned above, dredges require water and
are therefore not suited for desert or dry-placer areas.
Always consult with your local BLM, State Land, or Forestry
Department about the laws pertaining to dredging in your
area.
High-Banker
A
high-banker is basically a cross between a dry-washer and a
dredge. A high-banker is similar to a dry-washer because
material is shoveled in. The main difference being that
water is used to separate out the heavy concentrates instead
of air. A hose runs to the creek or river through which
water is drawn up to the high-banker via a water pump. This
water is then released over the sluice box. Gravel is
shoveled into a hopper which rests over the head of the
sluice box. A titled mesh screen allows gold-bearing gravel
to fall through into the sluice for processing. Rocks too
large to pass through the screen roll off onto the ground.
High-bankers utilize water as a means for separating gold
from worthless material; therefore recovery is good. They
can be used to retrieve gold from bench-type deposits, or to
process material that is a short distance away from a water
supply. High-bankers vary in both size and price. Some of
the portable, recirculating versions appearing on the market
are actually battery powered, which are a nice option for
small-scale sampling. High-bankers offer more flexibility,
as a prospector is not confined to working within the creek
or river itself, but like dredges, they depend entirely on
water and will be of little use in an arid environment.
You will discover that there are other types of mining
products available besides those listed above, so before
parting with your hard earned dollars, consider the
following questions: Where will this equipment be used? Will
water be available? What is my budget? And, on average, what
size is the gold? Once you know the answers, making a
decision will be a lot easier. Whatever equipment you settle
on, make sure you purchase from a reputable dealer. Someone
with personal mining experience, who is willing to answer
your questions and will maintain a good level of customer
service even after the sale has been made. I wish all of you
the best of luck with your prospecting! For more information
on finding placer gold, please visit the author’s website
at:
www.ArizonaOutback.com.
References:
Angier, Bradford (1980). Looking for Gold.
Harrisburg, PA: Stackpole Books.
McCracken, Dave (2005). Gold Mining in the 21st
Century. Chatsworth, CA: Keene Industries.
Gholson, Chris (2002). Rich Hill: The History of
Arizona’s Most Amazing Gold District. Tucson, AZ: Golden
Retriever Publications. |
