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Dredging for Gold
The modern suction dredge is one of the best placer gold recovery
units for being most gentle on the environment. It sucks up gravel
from the bed of the creek and redeposits it again a few feet away,
cleaned and sorted.
Nothing passes through the pump impeller
but water. The two systems in use for providing the suction for the
dredge hose are the ‘suction nozzle’ and the ‘power jet. The suction
nozzle type provides the suction right at the dredge intake. Both
have their advantages depending on the application.
Dredges need to prime both the pump intake piping and the suction
hose piping when using a power nozzle. This means making sure the
lines contain only water and are free of air.
The suction nozzle type is good for shallow water sampling, as the
intake hose doesn’t lose its prime if the intake handle is lifted
out of the water. The power nozzle type dredge has more suction but
needs to keep the intake hose submerged in order to keep its prime.
It works better for deep underwater mineral recovery.
A single operator dredging for sampling or small gold pay streak
recovery would use a dredge with a 5 inch or less sized intake
nozzle. Larger size suction dredges are employed in commercial/
industrial applications.
Proven Technology
Sometimes we need to take another look at what worked in the past.
Below is a sketch of a mining outfit used by a Cariboo miner. One of
the party who was shown where this gold deposit was located took out
a fortune using just such equipment. Would this setup be useful for
mining today?
First the things we wouldn’t do today.
Using a mercury covered plate would be out. Either than that the
only thing against using this outfit for gold recovery would be that
it would not work for in stream recovery. For that we would have to
wing dam or use a suction dredge. Another drawback would be that it
would only process about three cubic meters a day. For this
throughput we would have to have a fairly rich deposit, rich being
what you are willing to stick with to work. For those lower grade
larger size placer deposits it would take the bigger equipment.
On the other hand what has this rocker outfit got going for it
besides its historical proven reliability, lets make a list.
1.It is just the right size for those small higher grade deposits
that are too small in size for a larger operator to be willing to
set up for.
2. It can be used as a high banker or even for pocket deposits high
up in the watershed. A few 25 liter water jugs would supply it quite
nicely because of the recirculating water box. As a high banker it
wouldn’t need any pumps noisily running to supply it. A pump is also
limited by the length of supply hose needed not so this rocker
outfit. The water tank would conveniently provide a panning tub for
reducing the concentrates at the end of day as well.
3. This rocker outfit is portable. It would bungee well onto the
back rack of your atv mule. Usually you can get quite close to a
placer deposit using either the river, logging roads or cart and
game trails; for the last 100 meters you could carry this outfit. It
might take a couple of trips. A portability improvement I could see
would be to have a rocker and water box that would knock down into
boards and could be reassembled using wing nuts. Somewhere I heard
of a plan for a knock down rocker. If anyone has come across a
knockdown rocker in their research would they please let me know;
cal-ole@cablelan.net
4. The cost of building this equipment is low. One carpenter could
manufacture it. If you are handy with tools you can build the outfit
yourself. The replacement cost would be low if it was stolen or a
trigger-happy DFO Officer shot your other one to pieces. In some
areas apparently trigger happy DFO Officers in war surplus Desert
Storm helicopters can be a problem. When the outfit wears out it
could just be burned or left to nature to recycle. The outfit would
be bio degradable except for the punch plate which is easy to
transport out with your concentrates.
5. The cost of running the equipment would be minimal. No gas needed
for a pump and with the cost of gasoline these days it is a
consideration. The weight that would be taken up for gasoline could
be used to haul water for the recycle box. Also no costly big
equipment to maintain. This rocker outfit would run on bannock and
beans or if you find some better pay dirt maybe bacon and eggs.
Muscle power, don’t groan, I think you are up to it!
So there we have it; if your prospecting skills have reached a level
where you are finding small higher grade out- of - stream placer
deposits and your investment funds for recovery are limited think of
leveraging those investment funds by getting a low cost
recirculating rocker box outfit. It’s a low risk yet possible high
return investment. This outfit is light, portable and quick to get
up and running. Marry new tools like atv and gps with the proven
technology of this type of rocker outfit and this could be the year
you recover more than you ever dreamed possible.
Dry Washers
This method of placer mining has been used for years and years, even
before the gold pan. The first use of dry washing was with a
blanket. By tossing the gold bearing sand into the air the wind
would blow the lighter matter away, leaving just the gold on the
blanket. This was called winnowing. The winnowing method was
borrowed from farming where the harvested wheat was tossed in the
wind to remove the chaff from the grain.
The bellows method was used next. A bellows like that on the old
pipe organs was hand cranked producing wind to seperate the fine
sand from the heavier gold particles. This was all done in a dry
sluice box to collect the gold particles.
Methods then improved to gas driven dry washers that use an offset
impellor to make the 'wind' and cause a vibration to help
concentrate the materials in the riffles of a dry sluice box;
leaving behind just the gold to be collected up. |
