The upcoming season will be one that I will focus all my time working my claims in Montana. Spring melt off moves gold and I am anxious to find new pockets of color.
Snow is melting - I can't wait to get a pan in the creek. I am cleaning out my mining van, sorting out equipment, restocking supplies, batteries, etc. The following article from the BLM is worth a read. I have tried several home made sluice boxes and Long Toms and they work well with modern miners moss. . . . when starting out assembling mining equipment is a bit costly and if you are a do-it-yourself kind of individual, there are lots of helpful tools you can make yourself.
The dip-box is useful where water is scarce and where an ordinary sluice cannot be used because of the terrain. It is portable and will handle about the same quantity of material as the rocker.
Construction is relatively simple. The box has a bottom of 1- by 12-inch lumber to which are nailed 1- by 6-inch sides and an end that serves as the back or head. At the other end is nailed a piece approximately 1 inch high. The bottom of the box is covered with burlap, canvas, or thin carpet to catch the gold, and over this, beginning 1 foot below the back end of the box, is laid a 1- by 3-foot strip of heavy wire screen of about 1/4-inch mesh. The fabric and screen are held in place by cleats along the sides of the box. Overall length may be 6 to 8 feet, although nearly all gold will probably collect in the first 3 feet. The box is placed so the back is about waist high; the other end is 1/2 to 1 foot lower. Material is simply dumped or shovelled into the upper end and washed by pouring water over it from a dipper, bucket, hose, or pipe until it passes through the box. The water should not be poured so hard that it washes the gold away. Larger stones (after being washed) are thrown out by hand, or a screen-box can be added to separate them. Riffles may be added to the lower section of the box if it is believed gold is being lost.
Today, the rocker box is not used as extensively as the sluice box , but it is still is an effective method of recovering gold in dryer than usual areas. Like a sluicethe rocker box has riffles and a carpet in it to trap the gold. It was designed to be used in areas with less water than a sluice box. The process involves pouring water out of a pail and then rocking the small sluice box like a cradle, thus the name rocker box or cradle.
At least double volume of gravel can be worked per day with the rocker as with a gold pan. The rocker or cradle, as it is sometimes called, must be manipulated carefully to prevent loss of fine gold. With the rocker, the manual labour of washing is less strenuous, but whether panning or rocking, the same method is used for excavating the gravel.
The rocker, like the pan, is used extensively in small-scale placer work, in sampling, and for washing sluice concentrates and material cleaned by hand from bedrock in other placer operations. One to three cubic yards, bank measure, can be dug and washed in a rocker per man-shift, depending upon the distance the gravel or water has to be carried, the character of the gravel, and the size of the rocker. Rockers are usually homemade and display a variety of designs. A favourite design consists essentially of a combination washing box and screen, a canvas or carpet apron under the screen, a short sluice with two or more riffles, and rockers under the sluice. The bottom of the washing box consists of sheet metal with holes about 1/2 inch in diameter punched in it, or a l/2-inch-mesh screen can be used. Dimensions shown are satisfactory but variations are possible. The bottom of the rocker should be made of a single wide, smooth board, which will greatly facilitate cleanups. The materials for building a rocker cost only a few dollars, depending mainly upon the source of lumber.
After being dampened, the gravel is placed in the box, one or two shovelfuls at a time. Water is then poured on the gravel while the rocker is swayed back and forth. The water usually is dipped up in a simple long-handled dipper made by nailing a tin can to the end of a stick. A small stream from a pipe or hose may be used if available. The gravel is washed clean in the box, and the oversize material is inspected for nuggets, then dumped out. The undersize material goes over the apron, where most of the gold is caught. Care should be taken that not too much water is poured on at one time, as some of the gold may be flushed out. The riffles stop any gold that gets over the apron. In regular mining work, the rocker is cleaned up after every 2 to 3 hours, or oftener when rich ground is worked and gold begins to show on the apron or in the riffles. In cleaning up after a run, water is poured through while the washer is gently rocked, and the top surface sand and dirt are washed away.
Then the apron is dumped into a pan. The material back of the riffles in the sluice is taken up by a flat scoop, placed at the head of the sluice, and washed down gently once or twice with clear water. The gold remains behind on the boards, from which it is scraped up and put into the pan with the concentrate from the apron. The few colors left in the sluice will be caught with the next run. The concentrate is cleaned in the pan.
Skilful manipulation of the rocker and a careful cleanup permit recovery of nearly all the gold. Violent rocking should be avoided, so that gold will not splash out of the apron or over the riffles. The sand behind the riffles should be stirred occasionally, if it shows a tendency to pack hard, to prevent loss of gold. If the gravel is very clayey it may be necessary to soak it for some hours in a tub of water before rocking it.
Where water is scarce, two small reservoirs are constructed, one in front and the other to the rear of the rocker. The reservoir at the front serves as a settling basin. The overflow drains back to the one at the rear, and the water is used over again.
The capacity of rockers may be increased by using power drives. Such a device might be rocked by an eccentric arm at the rate of approximately forty 6-inch strokes per minute. The capacity of the typical machine with two men working is 1 cubic yard per hour. Where gravel is free from clay, the capacity may be as great as 3 cubic yards per hour.
A long tom usually has a greater capacity than a rocker and does not require the labour of rocking. It consists essentially of a short receiving launder, an open washing box 6 to 12 feet long with the lower end a perforated plate or a screen set at an angle, and a short sluice with riffles. The component boxes are set on slopes ranging from 1 to 1-1/2 inches per foot. The drop between boxes aids in breaking up lumps of clay and freeing the contained gold.
A good supply of running water is required to operate a long tom successfully. The water is introduced into the receiving box with the gravel, and both pass into the washing box.
The sand and water pass through the screen's 1/2-inch openings and into the sluice. The oversize material is forked out. The gold is caught by the riffles. The riffle concentrates are removed and cleaned in a pan. Quicksilver may be used to amalgam gold from the concentrate if the gravel contains very fine gold. Please note, quicksilver (mercury) is a hazardous substance and should only be used under controlled conditions and not released into the environment.
The quantity of gravel that can be treated per day will vary with the nature of the gravel, the water supply, and the number of men employed to shovel stones into the tom and then fork them out. For example, two men, one shovelling into the tom and one working on it, might wash 6 cubic yards of ordinary gravel, or 3 to 4 cubic yards of cemented gravel, in 10 hours.
A tom may be operated by four men; two shovelling in, one forking out stones, and one shovelling fine tailings away. Where running water and a grade are available, a simple sluice is generally as effective as the long tom and requires less labour.
From: Bureau of Mines Information Circular 8517 by J.M. West, released in 1971.