portion
than gold. At present the natives, both men and women, extract a
considerable proportion of the platinum by panning down the gravel
below the surface to as great an extent as possible and finishing it
on returning to the surface. The platinum is then bartered to the
traders for clothes and ornaments, and sometimes for money.
Many
efforts which have been made to institute large modern dredging
appliances have been baffled by two obstacles—the great freshets on the
river and the extremely insanitary conditions of the region. Fevers
prevail to an extent which is almost prohibitory for the work of any
but natives, yet it is probable that the occurrence of platinum in this
region is so great as to justify the sanitary measures taken in the
development of the Panama Canal for protection of the foreign workmen.
E. B. Kimball,1
in describing the primitive methods of working the platinum areas on
Atrato River and its tributaries to the south of the old trading center
at Quibdo, states that the gravel contains 90 parts gold to 10 parts
platinum. He attributes the gold and platinum to erosion of veins along
the flanks of the Andes Mountains. Besides gold-bearing quartz, he was
shown a specimen of a basic igneous rock, probably peridotite, carrying
native platinum in small, flaky particles.
In
the Daily Consular and Trade Reports of 1914, No. 62, Louis G. Dreyfus,
jr.. United States consular agent at Quibdo, Colombia, describes the
development of the Choco intendency and gives, in addition to much
general information, the following concerning gold and platinum mining:
The
gold-mining district extends from the junction of the Negua and Atrato
rivers south to the mouth of the San Juan. Almost all the deposits are
alluvial. There is at work in the field only one large company, formed
with British capital, which is extensively sampling with drills and
tunnels on Condoto River, an affluent of the San Juan.
Most
of the gold and platinum exported is obtained by native women, working
two or three hours per day. They use the antiquated ground-sluicing
process * * * to get rid of the coarser gravels, and then with their "
bateas " separate the metals from the sand and gravel. The batea is a
wooden pan, shaped like a very shallow inverted cone, 18 inches in
diameter and 3 inches deep at the center, with two small handles or
knobs on the rim. The women handle the bateas with great dexterity,
throwing off the gravel and sand by a rotary motion and leaving the
gold and platinum dust in the center. Another method of mining that is
extensively employed by these women is diving into 3 or 4 feet of water
for the sand and gravel containing the metals and bringing it up in the
bateas. This method is usually more remunerative than the sluicing
process.
The
gold workings have existed for centuries, but little has been done in
the development of the district. The river gravels were being washed by
the Indians long before the advent of the Spaniards, and this region
furnished much of the gold that was carried back to Spain. In those
days the value of platinum was unknown, and when the Indians brought
the metal down to the Spanish headquarters in Quibdo the platinum was
thrown away. Large finds of this discarded metal have been made
recently in Quibdo, and frequently the earth excavated for foundations
has yielded sufficient quantities of platinum to pay for putting up the
building. The natives were beginning to pan even the street, thus
uncovering large amounts of mud, which was injurious to health. A
decree was therefore promulgated in 1913 prohibiting any further
washing of earth in the streets of Quibdo.
Consular
Agent Dreyfus estimates exports of platinum at 542.4 pounds, or 6,509
ounces. In explanation of the fact that this is much less than the
figures usually quoted as the yield of platinum in
1 Kimball, E. B„ Mln. and Met. Soc. America Bull. 65, October, 1913.
