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OPAL IN AUSTRALIA |
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Geography:
The Water Problem |
| Leechman, in his book
entitled The Opal Book (R0384),
lists some 200 localities for opal in Australia.
These include the names of many mines, and
also localities in which the opal that is
called 'common opal' occurs - a type which
does not have the internal physical structure
to produce the play of colour of precious
opal. Most of the Victorian localities,
for example, would be of this type, and
that at Angaston, (the earliest report of
the occurrence of opal) is similar.
Some of the other localities are occurrences
of volcanic opal, i.e. opal occurring in
volcanic rocks. Occasionally the latter
may show a true play of colour; material
of this kind has come from localities such
as Springsure and Maleny in Queensland,
and Tintenbar and Rocky Bridge Creek in
New South Wales. Little commercial opal
has been produced from volcanic rocks in
Australia; it is usually rather transparent,
occurs in small pieces in vugs in the volcanics,
and tends to crack or craze readily. |
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| The major
opal fields occur around the southern boundary
of the Great
Artesian Basin, that area resulting
from a great incursion of the sea during
Cretaceous times. These localities are well
inland in very dry areas, which made the
exploitation of the deposits in the early
days a difficult and hazardous operation.
It has generated a special breed of people,
and the resulting settlements each have
a special character of their own. However
they do have certain things in common, apart
from the life of their people revolving
around and depending on, opal.
One of the major factors they have in common
is that they all occur in very hot, dry
areas of Australia, where shade temperatures
will often reach 45°C and more in summer.
The rainfall, especially in the South Australian
fields is very low; the average annual rainfall
at Coober Pedy, for example, is about 150
mm. In addition, the rainfall is very irregular,
and there can be periods when no significant
rain falls for two years or more.
The remoteness of these areas, accessible
in the early days by little other than bush
tracks, combined with the lack of water,
created difficult conditions for the miners.
The nearest towns, if some of them could
be glorified by that name, were hundreds
of kilometres away in some instances, so
that food and other supplies were slow in
arriving and expensive.
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| In the Lightning Ridge
area the problems of water supply in the
early days often caused disagreements between
local landholders and the miners. In drought
times almost the only source of water was
the dams built for stock; miners depended
on this water in difficult times, but the
landholders were often not co-operative.
It took some years of political lobbying
before the New South Wales government agreed
to build a dam to ensure a satisfactory
long term water supply for the opal mining
industry.
Water supply problems were overcome, at
least partially, by various means. Although
White Cliffs was in a rather isolated area
some 1000 km west of Sydney, it was only
about 85 km from Wilcannia, a small settlement
on the Darling River. Not only was the Darling
a reliable source of water, but it was also
a major artery for the transport of wool
and other agricultural products in the 19th
century. The Darling flowed into the Murray
River some 350 km to the south, itself Australia's
greatest river. The Murray flows for some
2500 km from the highlands in the southeast
of the continent, westwards to South Australia,
and then southwards until it empties into
the Southern Ocean. |
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| Although the Darling from
time to time dried up into discontinuous
pools of water, preventing river transport
for periods of time, there was always water
available for domestic requirements. The
water could be transported to White Cliffs
by horse or bullock-drawn tankers. Similarly,
other supplies could be obtained from Wilcannia,
as this was an important stagepost on the
Sydney to Broken Hill road. By the time
the opal field had become an important producer,
the great base metal mines of Broken Hill
had been exploited for some 20 years, and
this town had become by far the most important
in the far west of the State of New South
Wales.
The next major field to be developed was
Coober Pedy. This was some 1000 km north
of Adelaide, the capital of the State of
South Australia. Water supply was a particularly
difficult problem due to the low and intermittent
nature of the rainfall. Water of varying
quality was available from sub-artesian
bores, but good quality water had to be
brought some distance by tanker.
Later, the State Government constructed
concrete tanks into which rainwater could
be funnelled. This solved the basic problem,
although in drought times, water still had
to be brought in by tanker, by this time
motorised. Later, as part of a research
project, CSIRO (Commonwealth Scientific
and Industrial Research Organization, Australia)
built solar stills which produced a good
supply of high quality water for domestic
purposes.
The primary supply was from bores which
yielded mainly brackish (salty) water. In
recent years, this water has been purified
by the process of reverse osmosis.
Andamooka was established along a creek,
mostly dry, between low, rocky hillocks.
A well was dug which gave a small supply
of water, but in dry years it became necessary
to bring in water by tanker. By this time
it was the middle 1930's, so that motorised
tankers were available, and there was some
grading of outback roads by government authorities.
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