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Poor Man's Ore Mill
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Poor Man's Ore Mill
( Originally Published Early 1900's )
There is an ore mill that has been used in Mexico for hundreds of years, called the Arrastras, and with all the so-called modern improvements they can hold their own and better for good work. Their only fault is their lack of capacity. On the great Comstock vein in Nevada they continued their use long after they got their improved stamp mills, and in case a man of small means wishes to get some of the gold out of his mine for himself before selling, and has not the means to buy a lot of machinery, that perhaps would not be of much use to him anyhow, the Arrastras is all right. If you can get a little timber and a few hard, sharp stones they are cheap and handy. Of course it works best on free milling or soft ore and for clean work it is the best or as good as any.
It is made the same as an old-fashioned cider mill we used to grind our apples in. A circular pit about ten feet in diameter and from sixteen to eighteen inches deep is dug or built up of stone and clay or cement. Then the bottom of this pit is lined with good clay to about eight inches and pounded down hard. This pit is lined with hard sharp stones to the depth of eight or ten inches, making provision in the center for a shaft to set upright with an arm on it set into the shaft about a foot above the sharp stones. To this arm are fastened one or two flat, hard stones weighing from five to eight hundred pounds and having the ends raised two or three inches and fastened to the arm with eyebolts or wire. A sweep is attached to the post or upright and mule or horse power can be used. The circular pit must be watertight with an outlet or plug on the side and level with the bottom of the stone paring, also one at the level of the clay bottom.
To use the mill, break the ore into pieces about the size of hickory nuts and charge the mill with about 500 pounds of ore for a ten foot mill. Add a little water from time to time, also a couple of teaspoons of quicksilver for each four or five tons of ore. Grind this charge to a slush about as thick as cream. Now scatter in a strong ounce of quicksilver for every ounce of gold as near as you can guess, and your gold. pan sample shows. Grind two or three hours more, adding water and running slow until your slush is thin. Draw off the water from the plug at the top of the sharp stones, add another charge and repeat the operation, as it is not necessary to clean up oftener than every ten or fifteen days unless your ore is extremely rich or you need the money. Ten or fifteen turns a minute is fast enough to run the mill. When you make your clean-up draw off the water, wash off and remove the sharp stones and renew dull ones with sharp ones when you put them back. It is always well while grinding to throw in a little wood ashes to kill any soapy substance in the ore. This mill will have to be tried to be appreciated. It is also good to test a vein with if your prospective buyer wants a working test. After your amalgam is taken from the pit it will have to have the quicksilver squeezed out and then be retorted by the clay or potato process, or a retort made for the purpose. It is not necessary to throw away your quicksilver, if it gets dull after being used. If it gets in this condition it can be renewed by washing in a weak solution of sulphuric acid with a little zinc added.
As well as an ore mill one should have a stamp mill to break up his ore and here is one that will do the work well enough for a man of limited means, and breakages and repairs are not expensive. They cost nothing but a few bars of iron and a little rope and you can make it this way. Cut a log six feet long and eighteen or more inches in diameter and set it solid in the ground about two feet. Cut a hole six by six in the end and take some strong wrought iron pieces a half inch thick, eight or nine inches long and three inches deep. Set these in the top of the 6x6 inch hole about one half inch apart. This is for the grate. Now fit a box around your grate so pieces of the ore will not fly out. Now rig up your stamp as shown in the cut.
Procure a long springy sapling about four or six inches thru at the butt, make the butt flat and fasten it to the tree about five or six feet from the ground. Cut a post with a crotch on one end and set it in the ground about ten feet or so from the end. Cut another piece of timber about four feet long and eight inches through. Put an iron shoe on one end of this piece and an eyebolt in the other end and hang this on the end of your spring pole. This is your hammer and you now have a stamp mill that will do business if you have built it right.
Before closing this subject I would like to say a few words about the Klondike mines so called. These mines are, or were, a poor man's mines because they were placer diggings. The opinion is frequently expressed that there are no quartz mines there. Now I will venture the opinion that the gold found there is simply the float from immense outcrops and some day there, will be discovered by somebody some almighty quartz veins and they will run north and south and not parallel with the Yukon River. They may not be more than six inches under the tundra and they may be two thousand feet, and some day some one will be prodding around with a diamond drill and find things that will put even the great Comstock load in the shade and surprise the world. My reasons for thinking this would occupy too much space here and would not be understood by many.