Subject-specific learning materials (Part 1)
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Resource 1: Gold
Gold has been valued by mankind for thousands of years. In Australia
from the 1850s onwards gold has had a major impact on the fortune
of the country.
What makes Gold special?
Gold is a soft metal that is both ductile and malleable. This means
it is easily drawn into long wires and can be hammered into very
thin sheets. Gold is also an excellent conductor of heat and electricity.
It has a density of 19.3 gcm-3 and a melting point of 1064oC.
Gold is often described as benign. This means that gold is the
least reactive of the metals and so does not react with oxygen and
tarnish, like iron rusting for example.
This fact makes gold very important in many modern situations.
We are used to its role in money and decorative uses like jewellery
but gold also has very important uses in electronics and medicine,
avionics and industry.
There is only 1 stable isotope of gold.
Determine:
- The number of protons in the nucleus
- The number of neutrons in the nucleus of its stable isotope
- The arrangement of the electrons in the shells
The following sites are an excellent introduction to the properties
of gold:
How do we use gold?
Research the uses of gold and prepare a poster of this information.
Each use should be illustrated with a photograph.
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Resource 2: Finding Gold
Gold has been used by mankind for thousands of years. We know of
uses of hold that date back to 4, 000BC and since it can be found
lying on the ground, if you are lucky, it was also probably used
by prehistoric man.
A timeline of the important dates in the history of gold can be
found at The
Gold Institute: History.
So how can we find gold today?
To find gold it is usually best to start in regions that gold has
already been discovered. Gold nuggets are usually close to the surface
and can be located making use of a metal detector. The largest gold
nugget ever found was found only a few centimetres from the surface
at Moliagul in Western Australia. The Welcome Stranger, as it was
called, may even have been partially exposed. Scanning with a metal
detector, however, can not pick up gold if it fine gold sprinkled
through sand or gravel or contained in quartz.
Gold has collected in a region over many thousands of years. Usually
the gold has been transported by water and deposited as sediment.
A placer deposit is a concentration of a gold that has collected
in sediments of a stream-bed. The weight of gold means that it does
settle and accumulate in one place. This can be found by panning.
The gold pan is a shallow plate with sloping sides and flat bottom.
It is used to wash gold-bearing sediment. It is a slow process and
takes a lot of practice to effectively wash away the sediment leaving
behind the heavier gold, easily recognisable by its sun-yellow colour.
Over long periods of time material deposited in this way has been
compacted into rock and often formed into a lode of gold contained
in other rock.
Nowadays the gold in the streams is often due to slag or tailings
dumped from a large-scale commercial gold mining operation and been
washed downstream until it has collected.
Gold can still be found in waterways and large gold finds are still
sometimes made. Since the early 1800’s several gold rushes
have taken place around the world and many millions of people have
gone prospecting without much success. Most of the big sites have
probably been discovered by the big mining corporations, but...
Also visit: Prospecting
for Gold in the United States
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Resource 3: Mount Morgan - Setting the Scene
Gold was discovered on Ironstone Mountain by William Mackinlay
around 1870. When he went prospecting in the area in his spare time
he discovered the ironstone outcrop was gold bearing. He never developed
this site and it was not until 1882 that Tom and Ned Morgan visited
the area and pegged out a claim.
The full story can be found on this web site or at Mount
Morgan: The Discovery of Mount Morgan.
When the mine first started it was thought the ore could be processed
by amalgamation but this proved a costly mistake when it was realized
up to 75% of the gold was missed and had been washed down the river
with the waste tailings. In 1886 they switched to a chlorination
process. In 1902 high-grade copper was discovered and a smelting
process was established to collect the metal. In 1913 a concentration
plant was established, this included grinding, vibration, flotation
and eventually sintering.
The company then struggled as the quality of the ore dropped and
finally closed. A new company started in 1927, initially surviving
by pumping copper water out of the mine and collecting the copper
by precipitating. In 1932 open cut mining started. The concentration
mill was adapted to include froth flotation techniques. Between
1936 and 1944 cyanidation was used. In 1972 a flash smelter was
installed. In July 1981, production of ore from the mine ceased.
The flash smelter continued to operate till 1984. Between 1982 and
1990 a carbon-in-pulp cyanide plant was used to reclaim material
from tailings.
Mined for nearly 100 years, Mount Morgan yielded a total of 225,
000 kg of gold, 50, 000 kg of silver and 36, 0000 tonnes of copper.
(From Mount
Morgan: Treatment).
Research each of these processes in more detail. View the photographs
and equipment in the Mount Morgan Museum.
Water Quality Testing
To determine the exact impact of the mine on the local environment
we need to look at the effect on the local waterways; in this case,
the Dee River. The site Stream
Watch provides a useful guide to testing the quality of the
water. Samples need to be collected while visiting Mount Morgan.
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Resource 4: The Most Polluted River in Australia?
The River Dee flows through Mount Morgan before joining with the
Don, the Callide and the Dawson rivers. The water then flows out
to the sea via the Fitzroy River.
Acid Mine Drainage, or AMD, is the process where the sulphide containing
rocks that have been discarded as tailings or waste from gold or
copper mines reacts with oxygen and water to produce sulphuric acid.
Mount Morgan due to the size of the mine workings has produced considerable
amounts of slag waste and tailings.
The acid flow from the mine waste has considerable effect on the
Dee River and the aquatic species that live there.
| pH level |
Effect on aquatic species in
the Dee River |
| < 4.0 |
Fish species can not survive more
than a few hoursFew plant species can survive |
| 4.0 to 5.0 |
Most fish eggs will not hatch.Most
insects and frogs missing |
| 5.0 to 6.0 |
Bacteria begins to die |
| 6.5 to 8.5 |
Healthy conditions for most aquatic
species |
| 9.0 to 10.0 |
Harmful to fish if exposure is for
long periods |
| 10.0 to 11.0 |
Lethal to most fish if exposure
prolonged |
| > 11.0 |
Lethal to all fish |
- A pH of 7.0 is neutral
- pH < 7.0 is acidic
- pH > 7.0 is considered alkaline or basic
The river water is usually considered to be acidic when the pH
of the water is less than 5.0.
The quality of the water in the 18km downriver of the mine has
at times been recorded to have dropped to pH levels around 2.5.
The Queensland government commenced a project to determine the
best method of rehabilitating the mine site. Unless the problem
of the waste around the mine is solved then acid mine drainage will
continue to have an impact on the aquatic life of the Dee River.
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