What is the difference between open-pit and underground mining?

Open-pit (open-cut) mining strips the overburden and digs downward in benches from the surface; it suits large, relatively shallow deposits, is cheaper per tonne, and leaves a big surface footprint. Underground mining sinks a shaft and drives tunnels to reach deep or narrow ore bodies; it disturbs less surface but costs more and is more hazardous. The deposit’s depth and shape decide which is used.

What is the difference between a mineral resource and a reserve?

A resource is all of the material estimated to be in the ground. A reserve is the part shown, to a defined standard, to be economically and legally extractable under current conditions — in Australia, reported under the JORC Code. Because reserves depend on price and cost, a rise in a metal’s price can turn former resource into reserve without any new rock forming.

Finding & extracting resources

Q: How are non-renewable geological resources discovered?

By a mix of direct sampling and remote sensing. Direct sampling means physically getting the rock — mapping outcrops and, above all, drilling to recover a core that can be tested for grade. Remote sensing reads the ground from a distance using satellite images, aerial photographs and geophysical surveys (magnetic, gravity and seismic). Cheap, wide remote surveys flag anomalies; expensive, definitive drilling then tests the best targets.

Q: Did Aboriginal peoples mine in Australia?

Yes. Aboriginal peoples located and extracted geological resources for tens of thousands of years. Wilgie Mia in Western Australia is one of the oldest known ochre mines, and the Mount William greenstone quarry in Victoria supplied axe-head stone traded hundreds of kilometres, showing the same logic of locating, extracting and distributing a resource.

The useful metal is already in nearly every rock — the rare thing is having enough of it in one findable, reachable, affordable place. This powerbook follows that chain end to end: how rock becomes a resource, why deposits sit where they do, how we find them, how we get them out, and the single question that decides whether any of it is worth doing.

short sections

ways to find it

ways to get it out

Finding & extracting resourcesSection 1 of 6

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This book has 6 short sections. Read each one, answer the check, then use Next to move on — the bar above tracks how far you've come.

When does rock become a resource?

Almost every useful element is already all around you. Iron, aluminium, copper, even gold are present in ordinary rock — just spread so thinly that you would never notice. There is gold dissolved in seawater and scattered through the granite under your feet. The problem is never that an element is absent. It is that it is too dilute to be worth collecting.

A resource is what you get when a geological process has gathered one of those elements into one place, far above its everyday level — concentrated enough that digging it up and processing it makes sense. Rock carrying enough of a target metal to extract profitably is called ore, and how rich it is, is its ore grade. A workable gold deposit might hold a few grams of gold per tonne of rock: tiny, but hundreds of times richer than average crust, and that gap is the whole point.

These geological resources are non-renewable. The processes that built them ran over millions or billions of years, so each deposit is effectively a one-time inheritance — mine it out and it is gone. That single fact shapes everything that follows: finding, reaching and using these materials wisely matters because there is no second batch coming.

A deposit is the same rock with the useful part concentrated far above its everyday level.

New words

ore

Rock that contains enough of a wanted metal or mineral to be worth mining.

ore grade

How concentrated the wanted material is in the rock — the richer the grade, the less rock you move per tonne of product.

deposit

A spot where a useful material has been concentrated well above its normal level in the crust.

non-renewable

Formed over geological time and, for practical purposes, used up once extracted.

🔒 Lock it in

Why is gold being present in ordinary rock not the same as there being a gold deposit there?

Answer the check to continue

Quick reference & sources

The interactive book above is the lesson. What follows is a plain recap you can scan or revise from, plus the sources and how this maps to the syllabus.

Resource vs reserve, in one line

A resource is all of a material estimated to be in the ground; a reserve is the part proven, to a defined standard, to be economically and legally extractable right now. In Australia, reserves are reported under the JORC Code. The boundary between them is the cut-off grade, and it moves with commodity prices — so a price rise can grow reserves without any new rock forming.

Discovery: two families of method

Direct sampling physically recovers the rock — surface mapping and, above all, drilling to pull a core that can be assayed for grade. Remote sensing reads the ground from a distance: satellite images, aerial photographs, and geophysical surveys (magnetic, gravity, seismic). Remote methods are cheap and cover huge areas but only flag anomalies; drilling is definitive but expensive. Explorers use the first to aim the second.

Extraction: the deposit chooses the method

Large and shallow → open-pit (open-cut) mining, cheaper per tonne but a big footprint (much Australian iron ore and coal). Deep or narrow → underground mining via shafts and tunnels, costlier and more hazardous but less surface disturbance. Fluids (oil, gas) → drilling a well, onshore or offshore — as in Bass Strait and the North West Shelf.

Australia's position, and the first miners

Australia is one of the world's leading exporters of iron ore (largely from Pilbara banded iron formations, ~2.5 billion years old) and black coal (mainly Permian-age basins such as the Sydney and Bowen Basins) — geology and economics together. Extraction here is also ancient: Wilgie Mia in WA is one of the oldest known ochre mines, and the Mount William greenstone quarry in Victoria supplied axe-head stone traded hundreds of kilometres.

For HSC students

This powerbook covers the Geological Resources thread of Module 1 (Earth's Resources), framed by the inquiry question how are non-renewable geological resources discovered and extracted? Working through it, you should be able to:

relate a range of non-renewable resources (minerals, fossil fuels, economically significant ores) to where and how they form;
discuss the economic importance of Australia's non-renewable resources;
assess direct sampling against remote sensing techniques (satellite images, aerial photographs, geophysical data) for discovering resources;
compare extraction methods — open-pit mining, underground mining, and onshore and offshore drilling;
recognise traditional Aboriginal quarrying and mining as long-standing resource extraction.

Explanations here are original and are a study aid, not a copy of the syllabus. See the course hub for the full set of powerbooks and your progress.

Sources

Geoscience Australia — overviews of Australian mineral and energy resources, exploration methods (remote sensing, geophysics, drilling) and mining methods.
JORC — the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (the resource vs reserve distinction and cut-off grade).
Australian Heritage / WA and Victorian heritage records on Wilgie Mia (Weld Range ochre mine) and the Mount William (Wil-im-ee Moor-ring) greenstone quarry.
NSW NESA Earth and Environmental Science Stage 6 Syllabus (2017) — used only to scope the Module 1 "Geological Resources" content; explanations above are original.

Keep going

The metal was never the rare part. The rare part is one place where nature concentrated it, you can find it, and the price is right on the day you dig.