3. Ordinary ore, averaging about ½ 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.

On its arrival at the reduction works the ore is taken direct to the stamp
mill. At the Huanchaca works there are sixty-five heads of stamps, each
head weighing about 500 lb., with five heads in each battery, and crushing
about 50 cwt. per head per twenty-four hours. The ore is stamped dry,
without water, requiring no coffers; this is a decided advantage as
regards first cost, owing to the great weight of the coffers, from 2 to 3