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189 chapter xvi y How to Recognize Silver and Purify Metals If there is kindling (and the best to burn are the droppings from livestock because they create a stronger fire), make a fireplace and in the middle place some of the stones from the mine. Let them burn until they turn red in the way that iron does. Once they are red, throw them into cold water, each in a different place so that you can discern which of the colors has more silver. This will be obvious once they are in the water, since, if a stone has silver, it will sparkle throughout the stone like the heads of pins or little pieces of gunshot. It is also possible to recognize silver using lead in the following manner . When the ore is black, with few white veins (which, if there are many, use mercury), being very heavy, they are crushed so that the biggest pieces are the size of ground wheat. In a furnace, like a foundry where bells are cast, lead is added. Then the crushed rock is added. Half an arroba of lead will treat six libras of stone in this manner. Once the lead has melted and is glowing, throw in two libras of stone, placing the stone over the top of the lead. Once the stone has been completely mixed with the lead, continue adding the stone until all six libras are mixed. After all the stone or metal has been added, continue feeding the fire under the lead until the fire consumes the lead or turns it into little flakes that rise to the top. Remove these with a skimmer. Strike the sides of the vessel until the silver bursts forth from a bubble on the surface. Before doing anything, thrust at it three or four times as if you were opening and closing your eyes. Do this in the manner of making waves until everything opens and the silver is liquid and motionless. Then, put out the fire and the liquid silver will be a bit hard. Insert the skimmer at one side and move it around to the other in order to remove the silver from the container. If you want to test using mercury, use metals that are not black. If they are black, first burn them in an oven, moving them back and forth 190 Gold Mining until they release the malady of bitterness that black metal and stone contain. This burning should be done after they have been crushed. If any other metals contain bitterness, these should be burned as well. So, what I have said is that all metals or stone should be crushed and sifted to the size of wheat flour, and the sifter should be made of cloth. It will free the metals from each other. If there are six libras, add a handful of salt and mix everything together with water in the same way that someone mixes lime with sand. After it has been thoroughly mixed, make a small pile softened with water so that it absorbs the salt. Leave this as it is now on a board outside in the sun for four or five days. After these days have passed, pull apart the pile and sift the earth very well. On a good linen cloth pour two onças of liquid mercury and using the same cloth, hold it above the sifted earth and squeeze it. Kneed it with your hand for an hour. If it is very dry, add water until it obtains the consistency of clay used to make roofing tiles. After this, make a pile once more and put it in the sun for the same number of days. At the end of this period, if there is silver, it will be shown in the following way. That is, the mercury and the silver will be transformed into white flakes. If this occurs, add more mercury and mix again as before and place it in the sun for the same period. Then make it wet and mix it more. Once this is done, use an open polished gourd to scoop a small amount of this earth, the size of a nut. Wash this with clean water until the sand is cleaned from the gourd to determine if the mercury has adhered to all the silver. If it is still in flakes, add more mercury as done above. If the mercury has collected all the silver, it will not...

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