Ore Dressing, etc.—­This consists simply in the separation of the ore by hand at the mines into different qualities, by women and boys with small hammers, the process being that known as “cobbing” in Cornwall.  The object of this separation is twofold:  first to separate the rich parts from the poor as they come together in the same lump of ore, otherwise rich pieces might go undetected; and, secondly, to reduce the whole body of ore coming from the mine to such convenient size as permits of its being fed directly into the stamps battery.  The reason for this separation not being effected by those mechanical appliances so common in most ore dressing establishments, such as stone breakers or crushing rolls, is simply because the ores are so rich in silver, and frequently of such a brittle nature, that any undue pulverization would certainly result in a great loss of silver, as a large amount would be carried away in the form of fine dust.  So much attention is indeed required in this department that it is found requisite to institute strict superintendence in the sorting or cobbing sheds, in order to prevent as far as practicable any improper diminution of the ores.  According to the above method, the ores coming from the mine are classified into the four following divisions: 

1.  Very rich ore, averaging about six per cent. of silver, or containing say 2,000 ounces of silver to the ton (of 2,000 lb.).

2.  Rich ore, averaging about one per cent. of silver, or say from 300 to 400 ounces of silver to the ton.

3.  Ordinary ore, averaging about 1/2 per cent. of silver, or say from 150 oz. to 200 oz. of silver to the ton.

4.  Gangue, or waste rock, thrown on the dump heaps.

The first of these qualities—­the very rich ore—­is so valuable as to render advantageous its direct export in the raw state to the coast for shipment to Europe.  The cost of fuel in Bolivia forms so considerable a charge in smelting operations, that the cost of freight to Europe on very rich silver ores works out at a relatively insignificant figure, when compared with the cost of smelting operations in that country.  This rich ore is consequently selected very carefully, and packed up in tough rawhide bags, so as to make small compact parcels some 18 in. to 2 ft. long, and 8 in. to 12 in. thick, each containing about 1 cwt.  Two of such bags form a mule load, slung across the animal’s back.

The second and third qualities of ore are taken direct to the smelting works; and where these are situated at some distance from the mines, as at Huanchaca and Guadalupe, the transport is effected by means of strong but lightly built iron carts, specially constructed to meet the heavy wear and tear consequent upon the rough mountain roads.  These two classes of ores are either treated separately, or mixed together in such proportion as is found by experience to be most suitable for the smelting process.