Ausgeology. Senior secondary lessons

SACE Stage 2 Earth and Environmental Science · Topic 2: Earth’s resources

Ore deposits.

Most rock holds only a trace of any metal. An ore deposit is a place where natural processes have concentrated a metal enough for it to be mined at a profit. This lesson follows how that happens, how geologists find a deposit that is buried under hundreds of metres of younger rock, how it is mined, and what mining can leave behind.

Slide sideways to see the whole picture.

Illustration
One imaginary landscape holding the five ways ore forms and the three kinds of mine in this lesson. In real life they are in different places and formed at different times. Not to scale: the depths are squeezed and the deposits drawn far bigger than they are.
  • 1Dense crystals settle in a magma chamber (screen 2)
  • 2Hot fluids leave veins above a granite (screen 2)
  • 3Weathering leaves bauxite behind (screen 3)
  • 4Running water drops gold in a stream bed (screen 3)
  • 5An ocean without oxygen lays down banded iron (screen 4)
  • AOpen cut (screen 7)
  • BUnderground (screen 7)
  • CIn-situ leaching (screen 7)

Out of the ground

Geologists divide the things people use into two kinds: what is grown, and what is mined. Here is some of what is mined, in things you use every day, according to Geoscience Australia.

In a mobile phone

Iron, copper and aluminium, with traces of tungsten, silver, gold and cobalt, and of elements such as tantalum, niobium, germanium and rare earths. About 15 g of the phone is copper, and a little indium makes the touchscreen work.

Geoscience Australia: What makes a mineral critical? (2026) and Copper

In a house

An average family home contains more than 90 kg of copper: 40 kg of it in electrical wire and 30 kg in plumbing.

Geoscience Australia: Copper

In a car, a road and a railway

Steel, made from iron ore, goes into car frames and engine cylinders, railway carriages and engines, ships, bridges and buildings.

Geoscience Australia: Iron

Mining in Australia is older than mining companies

Long before colonisation, First Nations people quarried stone and mined ochre, and traded them over hundreds of kilometres. Three places where they did, described by museums and heritage records:

Wajarri Yamatji Country, Weld Range, WA

Wilgie Mia

A red ochre mine. At the time of European contact its ochre was traded far and wide across Aboriginal Australia, and it is still used in ceremony today. Wilgie Mia is on the National Heritage List.

WA Museum

Wurundjeri Country, about 60 km north-west of Melbourne

Wil-im-ee Moor-ring (Mount William)

Wurundjeri people quarried greenstone here to make blanks for stone hatchets, from 268 pits and shafts. The greenstone was traded up to 800 km away.

Australian Heritage Database; Museums Victoria

Adnyamathanha Country, northern Flinders Ranges, SA

Bookatoo (Parachilna)

A red ochre mine whose ochre was famous over a wide region of Central Australia. Dieri people, who lived 500 km to the north, sent parties all that way to barter for it.

Museums Victoria

What we are learning

How natural processes concentrate metals into ore, how to identify ore minerals, how a buried deposit is found and mined, what mining can do to waterways, and how long Australia’s resources might last.

I can

  • 1explain how gravity settling and hot fluids concentrate metals in and around a magma.
  • 2explain how weathering, erosion and deposition concentrate ores such as bauxite and placer gold.
  • 3explain how banded iron formations formed in an ocean without oxygen.
  • 4identify ore minerals from their physical and chemical properties.
  • 5explain how surveys and drilling find a buried deposit.
  • 6explain how a deposit’s size, shape and depth decide how it is mined.
  • 7describe how sulfide ores can harm waterways and the air, and how the harm is managed.
  • 8use data to compare how much different lifestyles use, and to judge how long resources might last.

SACE Stage 2 Earth and Environmental Science, Topic 2: Earth’s resources. This lesson covers the topic’s metallic and non-metallic mineral resources. Coal, oil and gas are in a separate lesson.

How this lesson works: a jigsaw

  1. Home groups of three. Each of you takes one of the three expert screens.
  2. Expert groups (screens 2, 3 and 4). Work through your screen with the others who chose it, and fill in the teach-back card at the end.
  3. Back to your home group (screen 5). Teach your process to the other two. Then identify the ores and match eight real deposits to the processes that formed them, which takes all three experts.
  4. From discovery to closure (screens 6 to 9). Find a buried deposit, choose how to mine it, follow its footprint and judge how long the resource will last.
  5. Show what you know (screen 10). Eight questions.

Working on your own? Do every screen in order. Your answers and notes are saved in this browser, so you can stop and come back.

Expert group A

Ore from magma

Dense crystals settle to the floor of a magma chamber; hot fluids from a cooling granite leave veins in cracks.

Expert group B

Weathering and water

Rain leaves aluminium behind as bauxite; a stream drops gold where the water slows.

Expert group C

An ancient ocean

Iron dissolved in an ocean without oxygen settles as banded iron formation, the start of the Pilbara’s iron ore.

My notebook

Printable activity

Survey grid

Two pages: map buried metal objects with a metal detector, or a phone’s magnetometer, over a measured grid, then choose where to dig. It goes with the survey on screen 6.

Activity sheet (PDF) Editable (Word)

AExpert group A

Ore from magma.

How can molten rock gather metals together?

In most magma, metals are spread thinly through the melt. Two processes can concentrate them: dense crystals or droplets sinking to the bottom of the magma, which is gravity settling, and hot, watery fluids carrying metals out of a cooling magma into cracks, which is hydrothermal activity.

Gravity settling needs a mineral, or a liquid, that is much denser than the magma around it, and enough time for it to sink before the magma sets solid. Hydrothermal fluids work differently: they do not depend on density, but on what a hot fluid can hold in solution and what it drops when it cools.

Key idea

Dense minerals can settle out of a magma into layers of ore. Hot fluids given off by a cooling magma can carry metals up into cracks, where they come out of the fluid as veins when it cools or reacts with the rock.

Why do magnetite crystals end up in a layer on the floor of a magma chamber?

Teach-back card: ore from magma

BExpert group B

Weathering and water.

How can rain and running water concentrate a metal?

At the surface, rain and running water break rock down and move the pieces. A metal can be concentrated in two ways: it can be left behind when the more mobile elements around it are dissolved and carried away, as aluminium is in bauxite, or it can be dropped by running water where the water slows, as gold is in a stream bed.

Australia is the world’s second-largest producer of bauxite, mined from open cuts at Weipa in Queensland, Gove in the Northern Territory and the Darling Range in Western Australia. Gove, near Nhulunbuy, has been mined since 1971.

Gold that has weathered out of rock is heavier than almost everything else a creek carries, so it is trapped where the water slows: on the inside of bends, behind obstructions, and in hollows and cracks in the bedrock. Alluvial gold in creek gravels drew the gold rushes of the 1850s, including those at Ballarat and Bendigo in Victoria. Where younger sediments or lava flows later buried an old gold-bearing stream bed, miners called it a deep lead.

Waves sort grains in the same way. Mineral sands are old beach, river or dune sands rich in rutile, ilmenite, zircon and monazite, hard minerals that resist weathering, with densities of 4 to 5.5 g/cm³. The waves carried the lighter quartz grains back to sea and left the heavy minerals behind on the beach. In 2024 Australia produced more rutile than any other country.

Key idea

Weathering and water concentrate ore in two ways: by carrying away the more mobile elements and leaving the immobile ones behind, as in bauxite, and by dropping dense grains where the water slows, as in placer gold and mineral sands.

Specks of gold and grains of quartz sand of the same size are carried down a creek in a flood. As the water slows on the inside of a bend, which is dropped first, and why?

Teach-back card: weathering and water

CExpert group C

An ocean without oxygen.

Why did so much iron settle on the sea floor billions of years ago?

The Hamersley Group in the Pilbara is the most economically important set of rock layers in Australia, because of its large iron ore deposits. Its iron began as banded iron formation, laid down on the sea floor when the oceans held almost no oxygen: an anaerobic environment.

Turn a piece of banded iron formation

Red bands of jasper, a form of chert, alternate with shiny grey bands of iron oxide. The bands are often folded, because the rock was squeezed long after it formed.

Key idea

Iron can stay dissolved in seawater that has almost no oxygen. Where oxygen made by cyanobacteria met that water, the iron formed insoluble iron oxide, which settled in bands with silica. Much later, fluids removed silica and added iron, turning some banded iron formation into the high-grade ore mined in the Pilbara.

Why are banded iron formations like the Pilbara’s not forming in the oceans today?

Teach-back card: an ancient ocean

5Back in your home group

Identify the ores.

How can you tell one ore mineral from another?

Take turns to teach your expert process to your home group, using your teach-back card. Then test the twelve ore minerals on the bench, name six mystery ores, and decide which process concentrated each of eight real deposits.

Colour alone is a poor guide. Pyrite, chalcopyrite and gold are all yellow and metallic, but their streak and hardness tell them apart: gold leaves a golden-yellow streak and dents rather than breaks; chalcopyrite leaves a greenish-black streak and a steel nail scratches it; pyrite also leaves a dark streak, but a steel nail cannot scratch it.

Which process concentrated it?

0 of 8 sorted

This takes all three experts. Choose the process for each deposit.

Key idea

Streak, hardness, magnetism, density and a few special tests tell ore minerals apart, even ones that look alike. Each kind of deposit, and so each process, tends to concentrate particular minerals.

A brassy yellow, metallic mineral leaves a greenish-black streak. A fingernail cannot scratch it, but a steel nail can. What is it?

My notebook

6From discovery to closure · 1 of 4

Find it.

How do geologists find ore that is buried under hundreds of metres of rock?

An ore body changes the ground around it. It can make the rock denser, more magnetic or better at conducting electricity, and where it is near the surface, metals from it spread into the soil, water and plants above it, where geochemical sampling can detect them. Surveys measure these changes from the air or the ground. Only drilling shows whether the ore is really there.

Key idea

Magnetic, gravity and electromagnetic surveys detect how an ore body changes the physical properties of the rock; soil sampling detects how it changes the chemistry near the surface. Each survey narrows the search, and drilling tests it.

In 1975 Western Mining Corporation drilled where gravity and magnetic highs coincided, and found Olympic Dam. Why aim for the place where both highs lined up?

My notebook

7From discovery to closure · 2 of 4

Mine it.

How do a deposit’s size, shape and depth decide how it is mined?

Most metal ore is mined in one of three ways. Which one suits a deposit depends on how deep it is, how big it is and what shape it has, and on whether the ore can be dissolved where it lies.

Open cut

  • A pit dug down from the surface in steps called benches.
  • All the waste rock above and around the ore has to be dug out too.
  • Suits big ore bodies at or near the surface, including low-grade ones.

Underground

  • Shafts or sloping tunnels called declines reach the ore.
  • The ore is broken and removed from spaces called stopes, and hoisted or trucked to the surface.
  • Suits deep ore bodies, and narrow or rich ones, because far less waste rock is moved.

In-situ leaching

  • A solution is pumped down wells, dissolves the ore minerals where they lie, and is pumped back up.
  • No pit or tunnels, but the ore must be in rock that liquid can flow through, held between layers it cannot.
  • Used for uranium in sand aquifers.

Choose the method

Three real deposits

Key idea

Big ore bodies near the surface suit open cut. Deep, narrow or rich ones suit underground mining. Ore in a permeable aquifer between impermeable layers can be dissolved where it lies. Depth matters so much because the waste rock that a pit must remove grows far faster than the ore it reaches.

Using the pit model, why does an open pit become less likely to pay as the ore lies deeper?

My notebook

8From discovery to closure · 3 of 4

The footprint.

How can mining harm waterways and the air long after the ore is gone, and how is the harm managed?

Many metal ores are sulfide minerals, and they are often found with pyrite, an iron sulfide. When sulfides meet air and water, they make acid. At Brukunga in the Adelaide Hills and Rum Jungle in the Northern Territory, acid and metalliferous drainage from mines that closed decades ago still has to be managed.

How acid drainage starts

Put the chain in order
The chemistry

Overall, pyrite reacts with oxygen and water to make orange iron(III) hydroxide and sulfuric acid:

4FeS₂ + 15O₂ + 14H₂O → 4Fe(OH)₃ + 8H₂SO₄

The reaction happens in several steps, and bacteria speed some of them up. Lime (calcium hydroxide or calcium oxide) neutralises the acid.

Adelaide Hills, South Australia

Brukunga

Pyrite and pyrrhotite were mined from an open pit from 1955 to 1972, for the sulfur to make sulfuric acid for superphosphate fertiliser. Drainage from the site reaches Dawesley Creek, a tributary of the Bremer River, which flows past Langhorne Creek into Lake Alexandrina. A lime-based treatment plant has run since September 1980, and the SA Government has managed the site since 1998.

SA Department for Energy and Mining; Armstrong and Cox (2005); Scott and others (2011)

About 105 km south of Darwin, Northern Territory

Rum Jungle

Uranium and copper were mined and processed here from 1954 to 1971, producing 3,530 tonnes of uranium oxide and 20,000 tonnes of copper concentrate. Acid and metalliferous drainage polluted the East Branch of the Finniss River. The site was first rehabilitated from 1983 to 1986, and a new stage of rehabilitation began in 2022 and is expected to take 15 years. The Traditional Owners are the Kungarakan and Warai people.

NT Government: Rum Jungle rehabilitation

West coast of Tasmania

Queenstown

Copper ore was smelted at Mount Lyell from 1896 until the smelters closed in 1969. Trees felled for the smelters, sulfur fumes from smelting the sulfide ore, and fires stripped the surrounding hills, and erosion followed, leaving the bare hills the town is known for. Sulfur dioxide from smelting can also make rain acid.

Companion to Tasmanian History (UTAS); Encyclopaedia Britannica; Schneider and others (2022)

Key idea

Sulfide minerals exposed in waste rock and pit walls react with air and water to make acid, which dissolves metals and carries them into creeks and groundwater, harming the plants and animals that live there. Smelting sulfide ores gives off sulfur dioxide. Treating the water can take centuries, so mines now plan for it before they open.

Mining at Brukunga stopped in 1972. Why does its drainage still need treatment today?

My notebook

9From discovery to closure · 4 of 4

How long will it last?

Are Australia’s mineral resources sustainable, and who uses them?

Ore deposits formed over geological time, so they are not replaced on any human timescale. How long they last depends on how much ore is known, how fast it is mined, and how much people use.

Different lifestyles, different footprints

Tonnes per person
Show the numbers as a table

A material footprint counts all raw materials, including crops, timber and fossil fuels as well as metal ores and other minerals, and gives them to the region whose people use the final products. The chart shows the UN’s figures for regions. Australia’s own estimate for 2024 is about 31.1 tonnes per person (Australian Bureau of Statistics, from a different dataset).

Years of supply

Geoscience Australia, 2025

Geoscience Australia divides the resources that are known and accessible for mining by one year’s production. The answer is the resource life: how many years the resources would last at that rate.

Show the numbers as a table

Work it out

Divide resources by production
“It is not possible to state with any certainty how long Australian, and world, resources will last”, Geoscience Australia says, because production rates vary, deposits can become economic or uneconomic, and new resources are rarely found at the same rate as old ones are used up. Its resource life figures are a snapshot in time, for general impressions only.Geoscience Australia, Australia’s Identified Mineral Resources 2025: Summary of reserve and resource life

Key idea

Mineral resources are non-renewable. Resource life compares what is known with what is mined, but it changes as prices, technology, discoveries and demand change. People in wealthy regions use several times as much material as the world average, so how resources are used is as much a part of sustainability as how many are left.

Geoscience Australia gives Australia’s copper a resource life of 145 years. What does that number tell you?

My notebook

10Show what you know

Show what you know.

Eight questions, one for each of the I can statements on screen 1. You get one try at each, so think before you tap.

Which pair of processes can concentrate metals in and around a magma?

Why is bauxite at Weipa, Gove and the Darling Range rich in aluminium?

What did oxygen from cyanobacteria do in the making of banded iron formation?

A black, metallic mineral leaves a black streak, and a hand magnet snaps onto it. What is it?

Which result would point best to a dense, magnetic ore body buried under 300 m of younger rock?

Uranium lies in loose sand that holds groundwater, between two clay layers, about 110 m down. Which method suits it, and why?

Which statement about acid and metalliferous drainage is correct?

Australia’s resource life for bauxite is 40 years, and the world’s is 65. Which conclusion is best supported?

Printable activity

Survey grid

Map buried metal objects with a metal detector, or a phone’s magnetometer, over a measured grid, then decide where to dig and evaluate your survey.

Activity sheet (PDF) Editable (Word)
For teachers

Curriculum

SACE Board of South Australia, Stage 2 Earth and Environmental Science Subject Outline (accredited for teaching at Stage 2 from 2018, reissued for 2025), Topic 2: Earth’s resources. NT students take the subject as part of the NTCET. The topic outline says:

Students investigate the formation of non-renewable mineral and energy resources; techniques used for their discovery; identification and extraction, and effects of the extraction; and use of these resources on ecosystems.

This lesson covers six of the topic’s seven Science Understanding statements, for mineral resources. Coal, oil and gas, and the seventh statement (the formation of non-renewable energy resources), are in a separate lesson.

People use the geological resources of the Earth to help satisfy their needs and wants.

  • Compare the use of geological resources in various lifestyles.
  • Discuss, using examples from a variety of cultures, ways in which geological resources are used.

Non-renewable mineral and energy resources are formed in various ways over geological time-scales, so are not readily replenished.

  • Discuss the sustainability of reserves of fossil fuels, and metallic and non-metallic resources.

The formation of non-renewable metallic mineral resources is related to their geological setting.

  • Explain how metallic ores may be concentrated by gravity-settling and hydrothermal processes.
  • Explain how the processes of weathering, erosion, and deposition may concentrate metallic ores.
  • Explain how the formation of iron ore (banded iron formations) occurred in an anaerobic environment.
  • Identify metallic ores, using their physical and chemical properties.

A variety of techniques can be used to discover deposits of mineral and energy resources and identify the extent and quality of these resources.

  • Discuss techniques for finding mineral resources, using magnetic and electromagnetic surveys, geochemical sampling, and drilling.
  • Explain how seismic and gravity surveys are used in petroleum exploration.
  • Discuss how the presence of a resource can affect the surrounding physical and chemical environment.

The depth, extent, and location of mineral and energy resources determine the method of extraction.

  • Describe the essential features of underground, open-cut, and in-situ leaching methods of extraction of mineral resources.
  • Explain how the size, shape, and depth of a mineral deposit influence the choice of extraction method.
  • Explain how petroleum, shale oil, coal, and coal-seam gas are extracted from the Earth in different locations.

The extraction and use of mineral and energy resources influences interactions between the abiotic and biotic components of ecosystems, including hydrologic systems.

  • Describe potential environmental impacts that can be associated with the extraction, use, and processing of mineral and energy resources.

Where the lesson covers them:

  • People use the geological resources of the Earth: screen 1 (resources in everyday things; First Nations quarrying and ochre mining) and screen 9 (material footprints of different regions).
  • Non-renewable resources and the sustainability of reserves: screen 9, for metals and one non-metallic resource (zircon). Fossil fuels are in the coal, oil and gas lesson.
  • Formation of metallic resources: screen 2 (gravity settling, hydrothermal veins), screen 3 (bauxite, placer gold, mineral sands), screen 4 (banded iron formation) and screen 5 (identifying ores; matching deposits to processes).
  • Discovery techniques and how a resource affects its surroundings: screen 6. Seismic and gravity surveys for petroleum are in the coal, oil and gas lesson.
  • Extraction methods and how size, shape and depth decide them: screen 7. The extraction of petroleum, shale oil, coal and coal-seam gas is in the coal, oil and gas lesson.
  • Environmental impacts: screen 8 (acid and metalliferous drainage; sulfur dioxide from smelting).

Science as a human endeavour runs through the lesson. Its key concepts in the outline include these, used on the screens shown:

New technologies improve the efficiency of scientific procedures and data collection and analysis. This can reveal new evidence that may modify or replace models, theories, and processes.

Screen 6: airborne geophysics and drilling at Olympic Dam; screen 4: new dating of the Pilbara ore bodies.

The use of scientific knowledge may have beneficial or unexpected consequences; this requires monitoring, assessment, and evaluation of risk, and provides opportunities for innovation.

Screen 8: Brukunga and Rum Jungle; screen 7: the clay layers that in-situ leaching relies on.

The acceptance and use of scientific knowledge can be influenced by social, economic, cultural, and ethical considerations.

Screen 7: the Olympic Dam open pit, approved but shelved for market reasons; screen 2: the debate over how the Bushveld chromite layers formed.

Assessment design criteria the tasks give practice for: IAE2 and IAE3 (the stream model, the survey maps and the resource life data), KA1 and KA2 (the checks and the deposit sort), KA3 (the footprint and supply screens) and KA4 (teaching back in the home group). The printable survey grid is a field practical for IAE2 to IAE4; for IAE1, have students design the grid spacing and method themselves before they start.

How the lesson is taught

The lesson is built as a jigsaw (Aronson and Patnoe, 2011). Each student in a home group of three becomes the group’s expert on one way ore forms, and the home group can only finish screen 5 by pooling all three. The jigsaw makes every student responsible for teaching part of the content, which suits a topic with several parallel processes.

  • Lesson 1: screen 1 together; form home groups and give out the expert screens.
  • Lesson 2: expert groups work through screens 2, 3 or 4 and complete their teach-back cards (about 35 minutes), then rehearse their explanation with their expert group.
  • Lesson 3: home groups teach back (about 5 minutes each), then screen 5: the bench, the mystery ores and the deposit sort. With a school ore kit, use the real tests alongside the 3D specimens.
  • Lessons 4 and 5: screens 6 and 7, then the printable survey grid as a practical outside.
  • Lesson 6: screens 8, 9 and 10.

Students working alone can do every screen in order. The teach-back cards then serve as a summary of each process.

Handle with care

  • Mining is many students’ families’ work, in the NT and SA especially, and uranium mining in particular is contested. The lesson sets out what the sources say about impacts and their management without telling students what to think about mining. Let students bring their own knowledge.
  • First Nations material on screen 1 uses only what museums and heritage records have published. Some knowledge about ochre mines is restricted, so the lesson gives only the public record: the Country, what was mined, and how far it was traded. To go further, invite local Traditional Owners, following your school’s protocols. Rum Jungle’s traditional owners are named as the NT Government names them.
  • Safety: hydrochloric acid tests are for the teacher to demonstrate. Do not test sphalerite with acid: it gives off hydrogen sulfide. Radioactive minerals such as uraninite should not be handled in class. For the survey grid, do not dig in school grounds unless the location of buried services has been checked; hiding objects under a sheet or in a sand pit avoids the need.

Misconceptions the screens target

  • Ore is rock made mostly of metal (screen 1). Ore is any rock that can be mined at a profit, and many ores contain only a small percentage of metal.
  • Heavy minerals are magnetic, or magnetism moves crystals in magma (screens 2 and 5). Density does the sorting; magnetite is one of very few strongly magnetic minerals.
  • Gold is always found as nuggets (screens 3 and 5). Most placer gold is fine specks and flakes, trapped where water slows.
  • All yellow metallic minerals are gold (screen 5). Streak and hardness tell gold, pyrite and chalcopyrite apart.
  • A survey finds ore (screen 6). Surveys find differences in the rock; only drilling confirms ore.
  • Open cut is always cheaper (screen 7). The waste rock grows much faster than the ore as depth increases.
  • In-situ leaching has no effect on groundwater (screen 7). It depends on the confining clay layers; at Honeymoon, a 1999 trial found leach solution had moved through a gap in the lower clay layer (Mudd, 2002).
  • Pollution stops when a mine closes (screen 8). Acid drainage continues for as long as the sulfides react.
  • Resource life is a countdown (screen 9). It is a snapshot that assumes nothing changes.

About the data and the pictures

  • All the cross-sections, the stream, the survey area and the pit are models, not surveys of real places. Each says what is stretched or simplified. The 3D specimens are drawn in code from mineral descriptions, not photographed.
  • Gravity settling: chromite layers of the Bushveld Complex as the best-studied example, and their disputed origin: USGS Scientific Investigations Report 2010-5070-E; Holness and others (2023), for settling; University of the Witwatersrand (2022), against. Kambalda: Frost (1992), UWA.
  • Hydrothermal deposits: Geoscience Australia, Gold and Tin mineral facts.
  • Bauxite: Geoscience Australia, Aluminium mineral facts; NT Government, Resourcing the Territory (Gove since 1971); production rank: Geoscience Australia, AIMR 2025 world rankings (2024 data).
  • Placers and mineral sands: Yukon Geological Survey (2011); Geoscience Australia, Gold, Tin and Mineral sands; State Library Victoria; rutile rank: AIMR 2025.
  • Banded iron formation: Geoscience Australia, Iron; Australian Museum; WA Museum; Geological Survey of WA (Hamersley Group, 2630 to 2445 million years); University of Colorado (2024); Courtney-Davies and others (2024), PNAS (ore bodies 1.4 to 1.1 billion years old).
  • Mineral properties: Handbook of Mineralogy (Mineralogical Society of America); gibbsite density for bauxite; gold streak: geology.com; acid tests: Missouri University of Science and Technology (malachite), Athabasca University (sphalerite); gold hardness: Geoscience Australia.
  • Olympic Dam: Esdale and others, geophysical case history (ASEG; 1975 discovery, 260 m of cover at the deposit, 17 mGal and 1600 nT anomalies); SA Department for Energy and Mining (about 300 m of cover; host; more than 450 km of roads and tunnels); BHP Draft EIS 2009, chapters 2 and 5 (sublevel open stoping; the proposed pit and its 300 to 350 m of pre-strip); BHP news releases, October 2011 and August 2012; BHP operational review, October 2026.
  • Super Pit: Northern Star Resources (1903 mines and workings; 1989); EPA WA referral for Fimiston South (2022) and EPA Report 1779 (pit size; the pits joined).
  • Honeymoon: SA Department for Energy and Mining; MESA Journal (depth, basal sand, clay layers); AusIMM (Yarramba Palaeochannel); Boss Energy ASX release, 22 April 2024; Mudd (2002).
  • Brukunga: SA Department for Energy and Mining; Armstrong and Cox (2005); Scott and others (2011, treatment timelines of 300 to more than 1,000 years). Rum Jungle: NT Government. Queenstown: Companion to Tasmanian History; Britannica; Schneider and others (2022). Some sources give 1953 for the start at Rum Jungle and 1970 for the end of smelting at Mount Lyell.
  • Material footprint: UN SDG Global Database, series EN_MAT_FTPRPC, 2022 values. Resource life: Geoscience Australia, AIMR 2025, Tables 3 and 6 (resources as at December 2024; production for 2024). GA divides accessible economic demonstrated resources by production and rounds to the nearest five years.

Answers at a glance

  • Mystery ores: 1 galena, 2 pyrite, 3 magnetite, 4 chalcopyrite, 5 haematite, 6 malachite.
  • Deposit sort: Kambalda nickel, settling; gold in quartz veins, hot fluids; Ballarat and Bendigo creek gold, weathering and running water; Weipa, Gove and Darling Range bauxite, weathering and running water; Hamersley iron ore, ancient ocean; tin around granites, hot fluids; beach mineral sands, weathering and running water; Bushveld chromite, settling.
  • Survey: drilling finds ore in cells M6 to O8, L7 and P7, under the overlap of the gravity and magnetic highs; the cells around them show altered granite, a sign that ore is close. The magnetic dyke runs from the south-west corner towards the north (columns C to J); the dense gabbro is around E4.
  • Mining: Olympic Dam, underground; Super Pit, open cut; Honeymoon, in-situ leaching.
  • Acid drainage chain: mining exposes pyrite; air and water react with it; sulfuric acid and dissolved iron form; the acid dissolves metals; the metal-rich acid water reaches the creek.
  • Resource life by hand: copper 108.02 ÷ 0.75 = 144.0 (GA: 145); gold 12,938 ÷ 284 = 45.6 (GA: 45); bauxite 3,969 ÷ 100.5 = 39.5 (GA: 40).
  • Checks: q-magma, denser than the melt; q-water, the gold; q-ocean, the oceans now contain oxygen; q-ores, chalcopyrite; q-find, other rocks cause one high but not both; q-mine, the pit widens as it deepens; q-foot, pyrite keeps reacting; q-last, at the 2024 rate, if nothing else changed.
  • Exit check: x1 settling and hot fluids; x2 high rainfall leached the mobile elements; x3 insoluble iron oxide; x4 magnetite; x5 gravity and magnetic highs together; x6 in-situ leaching; x7 keeps forming while sulfides meet air and water; x8 less long than the world’s at current rates.

Saved progress

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References

  • Aronson, E., & Patnoe, S. (2011). Cooperation in the classroom: The jigsaw method (3rd ed.). Pinter & Martin.
  • Armstrong, M., & Cox, R. (2005). Brukunga pyrite mine, South Australia. Proceedings of the 9th International Mine Water Association Congress.
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Sources

Word list