John has prospected for gold in Arizona 10 years. His experience taught him to deal with the terrain, heat, and gold fever. He makes tools.
Fundamental High Banker
There are two things common to gizmos designed to separate gold from heavy fines; water and agitation. All agitate, and nearly all use water. This write-up will discuss the mechanism of the high banker with attention paid to advantages and disadvantages.
The high banker is a device that cobbles two traditional machines of the Old West prospector. It is mainly composed of a hopper and a sluice. The hopper holds material and feeds it on to the sluice at an adjusted rate. Note that in a river or creek, the angle the sluice is held at does not have to be extreme due to the power of running water. Since the high banker is placed up on a bank, it is usually placed at a higher angle. Think about how steep a sluice can be clutched in running stream water where prospectors search for placer – not too steep. On the dry bank the rule is the box should be angled about 1 inch per foot. On some models there are adjustable legs, folding or telescopic. Then trial and error kicks in to maximize gold capture and waste processing
In a properly automated and educated world, then, machines may prove to be the true humanizing influence. It may be that machines will do the work that makes life possible and that human beings will do all the other things that make life pleasant and worthwhile.
— Isaac Asimov, Robot Visions
The Hopper Box
The hopper is located above the sluice box. It is a box with a grate in the bottom and water tube and/or dredge hose above with holes. This allows the small material to fall through to the sluice. There is also an opening or door at the outside that lets large material and rocks that are too big to be discharged. They wind up in a pile on the ground or in a bucket. The finer material with gold washes down the riffles of the sluice.
A Little More Physics
The water surface of a stream is irregular (or riffled) due to irregularities of sedimentary deposits at the bottom. This turbulence is mimicked in the sluice box by strips of wood, plastic, or metal, usually aluminum. They copy the action of naturally riffled water by creating barriers to the flow of water (slowing it down). With a decrease in speed, the gold and other heavy material get lodged behind the riffle. This trapped material is collected and later panned.
The portion of the high banker that is the sluice is simply a chute with small obstructions that slow the water periodically. There is usually a grate of some sort on top of a porous material that traps small gold particles. The grate is frequently made of metal (aluminum) but can also be plastic or other material.
Carpeting of many materials, silicone matting, continuous coiled vinyl loop filaments, and other materials are employed in the sluice moss under the riffles. The grate can be removed easily and the moss is removed and washed in a bucket. The fine material (hopefully with gold) in the bucket is then panned.
More Mechanical Elements
Attached to the hopper you will usually find a dredge hose or a recirculating pump. Depending on the size of material being blown into the hopper (sand, stones, and/or water), the high banker can process material from a suction dredge, or it can act as a recirculating sluice.
Another Sluicing Machine on A Smaller Scale
In places where the gold is very fine (experience tells you the size), having a recirculating sluice for your fines can speed up work immensely. For instance, instead of hauling rocks and pebbles and debris back to your camp, which can be very taxing, you can screen the material into a bucket and save time and energy. Instead of shoveling into the sluice, you are usually sitting next to a machine and pouring cups of dirt into it.
Most of the folks I know use a 1/8 inch screen to separate their pay dirt, also known as #8 mesh. That provides 64 holes per square inch. 30 to 100 mesh are the common fine classifiers used in placer gold sluicing. Since I don't have a number of different machines for handling fines, I stick with the #8.
In Arizona, my gold prospecting club members use these classifiers where there is flour gold and lots of small flakes. Then the material can be placed in a recirculating sluice, like the one below, with the gold being captured rather easily.
The process is similar to the high banker. A recirculating water pump is placed in a tube of water and pumped to the top of the sluice. The flow rate can be controlled. Everything about it is smaller than a high banker, while these fine recirculating sluices don't work with dredges.
In the old days, say the 19th century, placer prospectors were limited in what they could accomplish. Their tools would not deal with deep water; they had no diving tanks, dredges or easily-handled pumps.
By using a dredge to pull material from the middle of a river, we are now able to reach areas that the California prospectors of yore only dreamed of. The high banker allows the prospector to reach those hard-to-handle spots where gold may have settled.
With recirculating sluices, we can now more easily separate the fines. Whereas the old timers used just a pan, the average prospector can eliminate tedious labor and a lot of Ben-gay at night!
Technology has been a blessing to the gold prospector.
Treasurenet, the Original Treasure Hunting Website, August 17, 2013. Retrieved September 1, 2019 from http://www.treasurenet.com/forums/gold-prospecting/370672-please-explain-mesh.html
McCracken, Dave, The New 49'ers, True Life Gold Prospecting Adventure, June 1993. Retrieved September 3, 2019 from http://www.goldgold.com/gold-prospectingclassification-of-material-in-sluicing.html
Gold & Gem Gazette, March 22, 2017, Fine Gold and Mesh Sizes Part One. Retrieved September 4, 2019 from https://www.goldandgemgazette.com/fine-gold-and-mesh-sizes-part-one/
Instructables, A Recirculating Sluice Box for Gold Prospecting. Retrieved September 8, 2019 from https://www.instructables.com/id/A-recirculating-sluice-box-for-gold-prospecting/
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2019 John R Wilsdon
John R Wilsdon (author) from Superior, Arizona USA on October 26, 2019:
Bj Crow - Thank you. You're right. I have changed the drop.
Bj Crow on October 25, 2019:
It's actually one inch of drop per foot