MEXICAN METHOD OF EXTRACTING SILVER FROM ORES. The following is obtained from a cotemporary We will suppose the hacienda contains 50 arastras 12 feet wide each driven by two stout mules which will re duce twenty tuns per diem and necessitate the employ ment of 20 stamps of about 125 pounds each moved by 12 mules more. At 3 A. M. each arastra is charged with from 700 to 1000 pounds of ore sand from the stamps (de pendent on the degree of fineness) consisting of a mixture of all the ores obtainable from different mines-such mix ture invariably facilitating the reduction and diminishing of water
MEXICAN METHOD OF EXTRACTING SILVER FROM ORES. The following is obtained from a cotemporary We will suppose the hacienda contains 50 arastras 12 feet wide each driven by two stout mules which will re duce twenty tuns per diem and necessitate the employ ment of 20 stamps of about 125 pounds each moved by 12 mules more. At 3 A. M. each arastra is charged with from 700 to 1000 pounds of ore sand from the stamps (de pendent on the degree of fineness) consisting of a mixture of all the ores obtainable from different mines-such mix ture invariably facilitating the reduction and diminishing of water being added and this is an important point the grinding is continued for 23 hours or till the ' lama' -the pnlverized ore manifests no grittiness on being rubbed strongly against the thumb nail and till a ' tentadura' or trial sample after being washed out in a little basin leaves only an impalpable asient' or deposit of metal lic particles. Should the slightest coarseness be percepti ble more water is added to thin the' lama' and the fluid portion is drawn off' by a spigot leaving the coarser de posit to be reground with the next charge. The ore mud having been left to drain till it attains the proper consis tency is incorporated with 5 to 6 arrobas per monton (4 to 5 per cent) of salt or an equivalent amount of saline earth and spread out in round cakes of 25 to 100 mon tones in the pati'-a large courtyard well paved with flags. Here it is left to absorb and dissolve the salt and meanwhile portions are removed for the assay by which the adelition of quicksilver is regulated-the proportion be ing 7 to 8 pounds for every ponnd of silver present. The amount of silver obtained by a skillful manager is gener ally larger than that shown by excess arising from several causes which I have not space to enumerate. After remaining heaped up a greater or less space of time (usually 24 hours) the mercury is added in as fine a state each monton of ' magistral' calcined copper p
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