Finding Earth’s Wealth
Materials

Samples of magnetic and non-magnetic metallic minerals and their ore rocks

Samples of other non-metallic minerals and rocks

Small magnet tied to a thread

Rare earth or strong bar magnet

Spring Balance with 15 g sensitivity

Pieces of iron or steel ~ 100 g

Cardboard box or simple wooden frame

Tray ~ 10 cm deep

Sand to place in tray
Risk Assessment
Potential problems
Spring recoil
Preventative procedures
Wear safety goggles
PROCEDURE
Part 1
1.
Investigate the effect of a magnet near a selection of identified minerals.
a. Which ones will deflect a small magnet hanging from a thread?
b. Which have no magnetic field associated with them?
c. What patterns can you identify in the physical properties of minerals that are
magnetic, metallic, dense, or non-metallic?
2.
Investigate the effect of a magnet near a selection of rocks, some that are metallic
mineral ores and some that are not. What patterns now exist in the magnetism
differences?
Part 2
(Note: a stud finder, magnaprobe or metal detector can be used instead of constructing a
magnetometer)
1.
Put on your safety goggles. Make a simple magnetometer by suspending the magnet
from the spring balance. Create a carrier for the magnet from a cardboard box or
simple wooden frame. You must be able to read the spring balance scale without
touching it, and the magnet has to hang freely without touching the tabletop.
2.
Place one magnetic object in the centre of the tray. Make a note of its dimensions and
position. (You may like to use an OHP sheet for this, marked in a 1 cm grid with letters
and numbers giving you a simple grid reference.)
3.
Cover the object with ~ 1 cm of sand.
© State of New South Wales through the
NSW Department of Education and Training, 2007.
http://www.curriculumsupport.education.nsw.gov.au/index.htm
page 1 of 8
4.
Starting at the centre point along one edge of the tray, move the metal detector along
two perpendicular survey lines that intersect above the buried object. Record the
spring balance reading at 2 cm intervals. (See recording chart.)
5.
Repeat the survey measurements in both directions.
6.
Repeat the survey (step 4) with 3 cm of sand covering the object, and again with 5 cm
of sand.
7.
Replace the object with one of different proportions and/or shape and repeat the
survey (steps 4 and 5).
8.
Remove the magnetic object and carry out the survey with only sand in the tray. Make
measurements of compass deflections for sand depths of 1 cm, 3 cm and 5 cm.
ASSESSMENT
Task 1
(Note: a stud finder, magnaprobe or metal detector can be used instead of constructing a
magnetometer)
For each survey direction over the first object, plot a graph of magnetometer deflection with
distance. Choose a scale such that results from all 3 depths of sand, plus the survey with no
object, can be plotted on one graph. Indicate the actual dimensions and position of the
magnetic object in each survey direction. Submit these graphs and your answers to the
questions below for assessment:
1.
How precisely does the magnetic survey profile define the edges of the buried object:
2.
How does depth of the buried object affect the magnetic survey profile?
3.
How does the shape of the buried object affect the magnetic survey profile?
4.
What was the purpose of doing the survey without any buried objects?
Task 2
Geophysical Exploration
Use external resources to research one method of geophysical exploration. Find out:
 The basic technique and scientific principles used
 Typical applications
 Age, historical development or recent updates to the technology
 Benefits and limitations of the technique
 Environmental impact
 Types of careers and personnel involved
Make sure you provide a bibliography of the resources that you use and present the
information in booklet or poster form to be shared with others.
© State of New South Wales through the
NSW Department of Education and Training, 2007.
http://www.curriculumsupport.education.nsw.gov.au/index.htm
page 2 of 8
Name: _______________________________
Finding Earth’s Wealth – Recording Chart
Sand
Depth
Line
Number
With Object
1 cm
3 cm
1
2
1
Without Object
1 cm
3 cm
5 cm
2
1
2
1
2
1
5 cm
2
1
2
0 cm
2 cm
4 cm
6 cm
8 cm
10 cm
12 cm
14 cm
16 cm
18 cm
20 cm
22 cm
24 cm
26 cm
28 cm
30 cm
© State of New South Wales through the
NSW Department of Education and Training, 2007.
http://www.curriculumsupport.education.nsw.gov.au/index.htm
page 3 of 8
FINDING EARTH’S WEALTH
Teacher information
Suggested Time
1 x 45 minute period
Type
Small Group
Purpose
To simulate geomagnetic surveying in locating ore bodies
MATERIALS

Samples of magnetic and non-magnetic metallic minerals and their ore rocks

Samples of other non-metallic minerals and rocks

Small magnet tied to a thread

Magnet

Spring Balance with 15 g sensitivity

Pieces of iron or steel (not stainless steel) ~ 100 g

Small cardboard box or simple wooden frame

Plastic tray ~ 10 cm deep

Sand to place in tray
RISK ASSESSMENT
Potential problems
Spring recoil
Preventative procedures
Wear safety goggles
TEACHING SUGGESTIONS
 Part 1 is an introduction to this activity giving students an opportunity to look at the
magnetic characteristics and differences between various minerals and rocks. Provide
identified samples that include magnetic and non-magnetic minerals, rocks that are metallic
ores, non-metallic ores and those that are not used in mineral extraction. This essential step
can be omitted if carried out in a previous activity, or extended to look at other mineral
properties such as density and conductivity. These two properties are especially relevant
since they are the basis of gravity and electrical geophysical surveying methods.
 If natural magnetic samples of sufficient size are available, substitute those for the pieces or
iron or steel.
 The combination of magnet, spring balance and magnetic samples needs to be tried out
first. The magnet should hang freely in the air from the spring balance, and move
perceptibly when passed over the sample hidden in the sand. It may be necessary to change
either the spring balance sensitivity or magnet strength. A light and powerful magnet is
best, so that the force of magnetic attraction is large relative to its mass.
© State of New South Wales through the
NSW Department of Education and Training, 2007.
http://www.curriculumsupport.education.nsw.gov.au/index.htm
page 4 of 8
 This activity may be extended by having co-ordinates written on the plastic tray and
students are to provide the co-ordinates of the ‘ore’ body. Or different shaped ‘ore bodies’
are buried and students determine the shape of the ‘ore body’.
 The simulation activity could be extended or replaced by a field survey with equipment
borrowed from a local university or survey company. A precession magnetometer is fairly
simple to operate and provides data that could be used to demonstrate relative magnetic
properties around a school. Alternatively, if an area is available away from other sources of
magnetic fields (cable lines, steel in structures, etc.) the simulation can be scaled up. Larger
iron objects buried 10 – 20 cm under the surface will be detected by the magnetometer. A
full magnetic survey requires corrections and data analysis beyond the scope of these
expectations but students will easily grasp the fundamentals of the technique.
 After the activity show students maps of magnetic field strengths across Australia, New
South Wales or local area. These tend to be aeromagnetic data, which are collected
differently but the principles and conclusions are similar to ground based surveys. By looking
at the relative values in different regions, and identifying the most obvious patterns in the
field lines, broad conclusions are possible about the major ore-bearing regions and
structures causing the patterns. It is valuable to compare the magnetic data to a map
showing the main mining regions of Australia.
 An assessment task for this activity may require students to investigate other types of
geophysical surveying used for both mineral location and the basic structure of the Earth.
When assigning this task, provide a list of methods for students to choose from or assign
specific methods to each student. Ensure that a wide range is covered for students to learn
from one another.
 Simulations for other methods are more challenging. Making contact with a geophysical
surveying company would present opportunities for a field trip or invited speaker. Students
could speak with a geophysicist or technician, plus see other equipment.
BACKGROUND
The Earth’s magnetic field strength is a product of the global magnetic field plus variations
due to the composition and structure of localised crust and upper mantle. It is strongly
influenced by solar radiation and this effect will be incorporated into the recorded daily
variations. The resulting field strength varies temporally and spatially.
In geomagnetic exploration, data processing is carried out to correct for the daily and
seasonal field variations, and to remove any know regional effects to produce local anomalies.
These anomalies are due to the magnetic signature of underlying rocks. The anomaly may be
positive or negative relative to the region. Positive anomalies are assumed to be caused by
rocks bearing ores of higher magnetic susceptibility.
Geomagnetic surveying is only of benefit when the target ore is more magnetic than the
surrounding rock structure. This is one specific example of an exploration technique. Other
combinations of target material relative to host rock will require different exploration
techniques. This fundamental principle should be made clear to students during their research
assessment task.
© State of New South Wales through the
NSW Department of Education and Training, 2007.
http://www.curriculumsupport.education.nsw.gov.au/index.htm
page 5 of 8
ASSESSMENT
Student Assessment Strategies
1. The magnetic survey plots showing recorded anomalies above buried objects.
2. Short answer questions analysing survey plots.
3. Booklet or poster describing one method of geophysical exploration.
Answer to Questions
1. How precisely does the magnetic survey profile define the edges of the buried
object?
The anomaly in the survey profile is wider than the object. Edges are not
sharply defined – the magnetic profile curves.
2. How does depth of the buried object affect the magnetic survey profile?
Deeper objects have less change in the magnetic readings. (They might see
a wider curve shape.)
3. How does the shape of the buried object affect the magnetic survey profile?
The profile shape changes in the same way as the object’s dimensions.
4. What was the purpose of doing the survey without any buried objects?
To see if there was any change in the magnetic profile without a known
source – control values for the experiments.
Checklist for use with Survey Plots
Yes
No
Are all 4 graphs included?
Is the scale on each graph appropriate?
Are the graphs clearly labelled, with each survey identified?
Is the position of the magnetic body shown?
Was the survey method followed correctly?
Marking guidelines for Task 2
Level 1
Technical details Little or
of method
misinformed
technical details
Understanding
Limited
of
understanding
environmental
of impact
impact
Analysis of
Limited or
benefits and
incorrect
limitations of the analysis
method
Descriptions of
Limited mention
career
of career
opportunities in
opportunities
geophysical
exploration
Level 2
Limited technical
details
Level 3
Some technical
details
Level 4
Full technical
Details
Some
understanding of
impact
Almost complete
understanding
or impact
Analysis
contains some
errors or
omissions
Some details of
a few career
opportunities
Analysis
complete with
some details
lacking
Details or
listings of some
career
opportunities
Detailed and
multi-level
understanding of
impact
Considered and
detailed correct
analysis
© State of New South Wales through the
NSW Department of Education and Training, 2007.
http://www.curriculumsupport.education.nsw.gov.au/index.htm
Full details of
many career
opportunities
page 6 of 8
Syllabus Links
SCIENCE Years 7-10 syllabus
Outcome 4.3: A student identifies areas of everyday life that have been affected by
scientific developments.
Outcome 5.3: A student evaluates the impact of applications of science on society and the
environment.
Essential Content
Students learn
about:
Students learn to:
4/5.3 the
applications and
uses of science
a) identify and describe examples of scientific concepts and
principles that have been used in technological developments
(including Australian examples)
Outcome 4.6: A student identifies and describes energy changes and the action of forces in
common situations.
Essential Content
Students learn
about:
Students learn to:
4.6.9 magnetic force
a) describe the behaviour of magnetic poles when they are brought
close to each other
b) identify everyday situations in which magnets and
electromagnets are used.
Outcome 4.13: A student clarifies the purpose of an investigation and, with guidance,
produces a plan to investigate a problem.
Outcome 5.13: A student identifies a problem and independently produces an appropriate
investigation plan.
Essential Content
Students learn about:
Students learn to:
4/5.13.1 identifying data
sources
a) describe a problem and develop an hypothesis or question
that can be tested or researched
b) propose possible sources of data and/or information
relevant to the investigation
c) identify what type of information or data need to be
collected
d) justify why particular types of data or information are to be
collected
e) identify the appropriate units to be used in collecting data
f) recommend the use of an appropriate technology or
strategy for collecting data or gathering information
g) formulate a means of recording the data to be gathered or
the information to be collected.
4/5.13.3 choosing
equipment or resources
a) identify advantages and limitations of using particular
laboratory and field equipment for a specific task
b) select appropriate equipment (including safety equipment)
and/or resources to perform the task
c) describe ways to reduce the risk to themselves and others
when working in the laboratory or field.
© State of New South Wales through the
NSW Department of Education and Training, 2007.
http://www.curriculumsupport.education.nsw.gov.au/index.htm
page 7 of 8
Essential Content
Students learn about:
Students learn to:
4/5.15 gathering first
hand information
a) make and record observations and measurements accurately
over a number of trials
b) use independently a range of data collection strategies and
technologies such as data loggers.
Stage 6 – Earth and Environmental Science syllabus links
Option – Mining and the Australian Environment
1 The relationship
between minerals
and geological
formations
indicates where to
search for ore
4
The exploration
and evaluation
of a named ore
deposit
Students learn to:
Students:
 identify the main geological
features of two Australian mineral
provinces including:
 solve problems, identify data
sources, gather and analyse
information from secondary
sources to identify the
geological settings and main
features of the chosen
mineral provinces
-
a base/precious metalproducing locality in an
island arc terrane, and
-
one selected from an iron
ore-producing locality in
an ancient continental
area or an area of
sedimentary ore formation
Students learn to:
Students:
 outline the common exploration
methods used to identify the ore
deposit (including satellite
imagery, aerial photograph
interpretation, geophysics,
geochemistry and drilling)
 gather information to
describe the impact of
improvements in technology
on exploration techniques
 plan and perform first hand
investigations to test for the
presence of ore minerals or
metals using:
-
a geophysical method
a geochemical method
© State of New South Wales through the
NSW Department of Education and Training, 2007.
http://www.curriculumsupport.education.nsw.gov.au/index.htm
page 8 of 8