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Gold prospectors
Panning for ‘gold’ in river sediment
Set up one or more tubs, about half full of clean
water, as shown in the first photograph. The tub
contains some washed sand, with a sprinkling of
crushed pyrite (‘fool’s gold’) scattered throughout.
(Brass filings may be used in place of pyrite, so
long as there are no jagged edges). Pupils should
take turns at panning for ‘gold’, to see how much
they can extract in a given time. Credit is given for
clean samples, with no sand remaining in the pan.
If you have enough, pupils may wish to keep their
‘gold’ to show their parents: otherwise, they
should return it to the tub.
You may need to show them what to do, by
pouring a small jug full of sand/‘gold’ into the pan,
with plenty of water. The pan is gently swirled
round with a circular motion, or jiggled from side
to side, to discard the sand, whilst retaining the Gold nuggets in the pan, Alaska, USA
denser ‘gold’. Water is added repeatedly and the AlaskaMining at en.wikipedia CC-BY-2.5;
process continued until all the sand has been GNU Free Documentation License
washed back into the tub, leaving the dense
‘gold’. Encourage your pupils to experiment to find
the most effective method.
A gold prospector in Madagascar, using a home-made pan
Lebelot, GNU Free Documentation License, Version 1.2
A young prospector in action Peter Kennett
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The back up
Title: Gold prospectors Context: This activity may be used in the context
of sedimentary processes in a geology lesson, or
Subtitle: Panning for ‘gold’ in river sediment as an application of a physical property in a
physics lesson. The technique is still actively used
Topic: Investigating how prospectors use the across the world where minerals are exploited, on
property of density to search for gold in river a wide range of scales, and is not limited to
th
sediments. bearded 19 Century prospectors in the
backwoods of the USA or Australia!
Age range of pupils: 5 – 85 years
Following up the activity:
Time needed to complete activity: 10 minutes • Try the Earthlearningidea activity, ‘Riches in
the river’ to demonstrate how the gold may
Pupil learning outcomes: Pupils can: have become concentrated in the river sand in
• develop motor skills as they experiment with the first place: also to investigate other ways of
the best method of separating materials; separating ores from sand.
• explain why density is a useful property in the • Carry out a web search for the techniques
separation of materials; used by mineral extraction companies to
• use their imaginations to visualise a real gold separate an ore from the waste. This will
prospector in the field. include the process known as froth flotation.
1
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• Carry out a web search to find the average • Gold panning is used as a small scale
concentration of gold in the Earth’s crust and commercial activity, but is also invaluable
to find examples of major gold deposits, where when prospecting for large scale deposits
it has become many times more concentrated where machinery will later be used to extract
in sedimentary deposits. the gold.
• Find out the current price of gold from a
financial newspaper. (In California, in 1852 it Thinking skill development:
was around $15 per ounce). Pupils develop the best technique for panning for
‘gold’ (construction).
Underlying principles: They reason why the ‘gold’ remains behind
• Gold originates in veins, usually in association (metacognition) and apply their findings to the
with other minerals such as quartz. It may be commercial world (bridging).
mined directly from such veins.
• Erosion of gold-bearing veins results in the Resource list:
gold being carried down rivers until it is • gold pan – either a commercial one as shown,
deposited along with the river sediment. or a shallow pan, such as a frying pan
• Ores such as gold, which become • washed medium-grained sand
concentrated by moving water, are called • particles of crushed pyrite or brass turnings.
placer deposits. The pyrite is crushed between two hammers,
• Because of its high density, the gold is followed by sieving through a kitchen sieve to
concentrated in favoured areas of the river remove the larger fragments, which are re-
bed, such as on bends and in the trough areas crushed. Aim for a particle diameter of 2mm or
of ripple marks. less.
• Prospectors concentrate the gold much further • small jug for scooping sand/pyrite mixture
by panning. • large tub, e.g. half of a wooden barrel or a
• The density of pure gold is up to twenty times large plastic container
that of water, whereas quartz sand has a • water
relative density of only 2.7.
• Pyrite has a relative density of about 6 – much Source: This version by Peter Kennett of the
higher than that of sand, but very much less Earthlearningidea team. The activity is commonly
than real gold. used at educational activity centres connected
with mining museums.
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