Page 73 - Handbook of Gold Exploration and Evaluation

54 Handbook of gold exploration and evaluation

the `great rushes' took place in the 1890s in the Klondike River, a tributary of
the Yukon River, Alaska. Klondike placers that became particularly famous for
their richness were `Rabbit Creek' (later known as Bonanza Creek) and
`Eldorado'.
The Klondike gold rush was, arguably, the most disastrous in terms of lives
lost on trails leading into the various diggings and had a character of its own.
Nolan (1980) epitomises two scenes, in particular, in the Klondike:
· newspapers crammed with advertisements for gold detecting machines; offers
of trained rodents for burrowing for gold, and slot machines for use with gold
nuggets
· after the rush ended ± the frozen bodies of two men in a derelict hut on the
Porcupine River. They had travelled in a great semicircle spanning 6,430 km
but were still hundreds of kilometres from the goldfields. In a pot hanging
over the long dead ashes of their fire, embedded in a cake of ice, was found a
half-cooked pair of moccasins.
The gold of the gold rushes was mainly alluvial and, while many of the early
techniques were little advanced from those of the Roman Empire, later
developments took the form of improved sluicing arrangements, rocker cradles
and horse-drawn puddling machines. In Australia, miners used devices called
`flycatchers'. These devices were based upon the `Golden Fleece' technique to
catch finely divided and flaky gold floating across the riffles of sluices con-
structed across the downstream creek bed. The flycatchers consisted of weirs, on
which were placed boards covered with blankets or sacking. The blankets were
taken up at intervals and washed to recover the gold.
By the end of the 18th century the great alluvial goldfields of the Americas
and Australasia were practically exhausted and the growing global demand for
gold could be satisfied only by increased and sustained production. Problems
associated with declining ore grades, more finely divided gold, increased
overburden depths, rocketing labour costs and increasingly strict controls for
environmental protection had to be faced up to for the first time. The Comstock
Au, Ag lode was discovered in Nevada in 1859 and as a result, Nevada was
proclaimed a State five years later.
Discovery of the Witwatersrand goldfield in South Africa in 1866 then
opened up the largest concentration of gold ore deposits known to mankind. The
main reef was apparently found by accident one Sunday morning by George
Harrison and George Walker. Within a week it was recognised by some as being
of unprecedented significance. But, as throughout Witwatersrand history,
opinions on the origin of its gold and deposit potential differed widely. Only
four weeks later, one expert reported that the auriferous reefs would not continue
to depths below 10 to 15 feet from the surface. A year later another expert,
Gardner Williams, stated categorically that the conglomerates were merely
surface deposits along ancient shorelines and that no confidence could be placed