Chapter 15
Riches in Rock: Mineral Resources
LECTURE OUTLINE
earth
Portrait of a Planet
Third Edition
©2008 W. W. Norton & Company, Inc.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Riches in Rock:
Mineral Resources
Prepared by
Ronald Parker
Earlham College Department of Geosciences
Richmond, Indiana
Mineral Resources

Minerals from the crust that are used by civilization.
Minerals are present in almost everything we use.
 They are utterly necessary for modern industrial society.


Two major categories.
Metallic.
 Nonmetallic.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Mineral Resources

Mineral resources form by geologic processes.
Occurrences are predictable.
 Formation is usually very slow.


Minerals are effectively nonrenewable resources.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Mineral Resources
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Mineral Resources

Two major categories.

Metallic.
Gold.
Silver.
Copper.
Lead.
Zinc.
Iron.
Aluminum.

Nonmetallic.
Sand and gravel.
Gypsum.
Halite.
Dimension stone.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
What Is a Metal?
Opaque, shiny, smooth, conductive solids.
 Metal properties from metallic chemical bonds.

Delocalized electrons move from atom to atom easily.
 Electron fluidity creates electrical conductivity.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
What Is a Metal?

Properties due to crystal structure and bonding.
Metals may be extremely hard (titanium) or soft (copper).
 Ductile – Able to be drawn into thin wires.
 Malleable – Able to be pounded into thin sheets.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
What Is a Metal?

3 categories.

Native – Naturally occur in pure form.
Copper (Cu)
Silver (Ag)
Gold (Au)

Precious – Rare and economically important.
Gold (Au)
Silver (Ag)
Platinum (Pt)

Base – Commonly used in industry.
Iron (Fe)
Lead (Pb)
Zinc (Zn)
Tin (Sn)
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
The Discovery of Metals
Native metals occur naturally in a pure form.
 Native metals are rare and durable. They include…

Gold.
 Silver.
 Copper.
 Iron.


We have utilized native metals for 1,000s of years.
Tools – They are easily shaped by cold working.
 Money – Chosen because of rarity and durability.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
The Discovery of Metals

Quest for native metals important in human history.
Native American copper trade.
 Spanish Conquistadors.
 California and Klondike gold.


Today, minerals underpin the wealth of nations.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Metals
Native metals are too rare to be mine sources.
 Instead, we use minerals that contain metals.

Metal ions are bonded to non-metallic elements.
 Ore minerals rarely resemble the pure metal.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Smelting

Releases metals from the mineral.

Different minerals require…
Different smelting techniques.
Different temperatures.

Nonmetallic waste is called slag.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Smelting
Steel is made from iron smelted with carbon.
 Blending molten metals creates alloys.

Alloy properties differ from pure metals.
 Bronze – An alloy of copper and tin.
 Brass – Copper alloyed with zinc.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
What Is an Ore?

Rock with a concentration of metal-rich minerals.
Present in enough abundance to be economic to mine.
 Metal must be readily extracted from the mineral.
 There are many different ore minerals.


Ores form via geological processes.
Magmatic activity.
 Hydrothermal alteration.
 Secondary enrichment.
 Sedimentary processes.
 Weathering processes.
 Hydraulic sorting.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources

Common ore minerals.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Geologic processes often concentrate metals.
Concentration must be high enough to yield a profit.
 The amount of useful metal present is the ore grade.
 The amount of enrichment required differs by metal.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Geologic processes generate mineral resources.
A dominant control is exerted by plate tectonics.
 Tectonic effects are overprinted by the hydrologic cycle.


Ore formation requires large amounts of time.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation
Mineral resource occurrence is predictable.
 Ores are not equitably distributed.

Some countries have many mineral resources.
 Other countries lack resources.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Magmatic ores.
Sulfide minerals crystallize early and sink in magma.
 Form massive sulfide ores at the bottom of chamber.
 Sulfides include…

Pyrite.
Chalcopyrite.
Bornite.
Galena.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Hydrothermal deposits.
Minerals deposited by hot, chemically active fluids.
 Common in rocks heated by plutonic intrusions.
 Often crystallize in rock fractures as vein deposits.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Hydrothermal deposits.

Black smokers - Occur along all mid-ocean ridges.
Seawater in cracked hot crust is heated, picking up metals.
Water cycles back to the cold ocean, metals crystallize out.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Hydrothermal deposits.

Mississippi Valley-type (MVT) ores.
Orogenic belts “squeegee” hot water through deep basins.
The hot water leaches minerals and carries them along.
Where basin brines surface and cool, they deposit metals.
MVT lead-zinc (Pb-Zn) deposits.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Secondary-enrichment deposits.
Ground water leaches and oxidizes primary sulfide ores.
 Adding O2, OH, and CO2, some secondary ores are prized.

Malachite.
Azurite.
Turquoise.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Sedimentary deposits.

Banded iron formations (BIFs).
Layered specular hematite (Fe2O3) and red chert (jasper).
Found globally 2.5 – 2 Ga with O2 buildup in atmosphere.

Manganese (MnO2 )–rich nodules.
Rich in trace elements, these grow slowly on the seafloor
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Residual mineral deposits.
Form via extreme (tropical) chemical weathering.
 Intense weathering strips almost everything out of soil.
 Residual lateritic soil is enriched in Fe and Al oxides.

Bauxite – Primary ore of aluminum.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Ore Formation

Placer deposits – Concentrated by flowing water.

In high-velocity water…
Low-density minerals are suspended and washed away.
High-density grains are concentrated by settling out.
Important for gold, tin, and iron.
 Best preserved in fossil
stream sediments.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Mineral Exploration

Ores are located by evidence of metal enrichment.
Color – Enrichment often discolors rock and soil.
 Geophysical surveys – Magnetism, gravity, radioactivity.
 Geochemical surveys – Ore can be found by chemical
analyses of water, stream sediment, soil, and biota.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Mineral Exploration

Ore present in a deposit is assessed by...
Geophysical measurements.
 Core drilling.
 Geochemical analyses.


If economic, a deposit is
developed for mining.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Mineral Production
Open-pit mines – Large excavations open to the air.
 Less expensive and dangerous than tunnel mines.
 Usually require ore within
100 m of the land surface.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Mineral Production

Underground mines – Ore obtained by tunneling.
Tunnels are linked to a vertical shaft (an adit).
 Ore is removed by drilling and blasting.
 Excavated ore is hauled to the surface for processing.
 Expensive and dangerous.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Nonmetallic Resources

Materials that lack metals are used by humans.
Dimension stone – Rock slabs used as building material.
 Crushed stone – Material for roads, asphalt, and concrete.
 Cement – Mixture of heated limestone, quartz, and clay.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Nonmetallic Resources

Nonmetallic minerals commonly used in homes.
Calcite – Base material of cement (concrete).
 Clay minerals – Used for bricks, pottery, dishware.
 Gypsum – Most common material in wallboard or plaster.
 Quartz – Used to make window glass.


U.S. per capita nonmetallic mineral use is huge.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Global Mineral Needs

Mineral resources are nonrenewable.
They form as the result of geologic processes.
 These processes are too slow to generate new deposits.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Global Mineral Needs

Mineral resources are not evenly distributed.
Some countries are mineral-rich; some are mineral-poor.
 This is a particular issue for strategic mineral resources.

Metals needed for highly specialized applications.
National security and defense.
Aerospace.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Global Mineral Needs

How long will current mineral resources last?


Depends upon consumption rates and reserve amounts.
Some mineral resources will run out soon.
Global resources of Pb, Zn, and Au?
 U.S. resources of Pt, Ni, Co, Mn, Cr?

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
< 30 years.
<1 year.
Chapter 15: Riches in Rock: Mineral Resources
Global Mineral Needs

Continued use of scarce minerals will require…
Discovery of new sources.
 Increase in price to make hard-to-get reserves profitable.
 Increased efficiency and conservation.
 Substitution.
 Recycling.
 Doing without.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Environmental Issues

Extraction and processing has large impacts.
Air.
 Surface water.
 Ground water.
 Soils.
 Biota.
 Aesthetics.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Environmental Issues

Acid mine drainage (AMD).
Sulfides exposed to O2 create sulfuric acid.
 Water from spoil piles is acidified (pH < 5.7).
 AMD creates toxic conditions.

Mobilizes heavy metals.
Kills stream organisms.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
Environmental Issues
Spoil – Material removed to expose ore.
 Tailings – Mineral processing wastes.
 Both have large adverse environmental impacts.

Acid leachates contaminate ground and surface water.
 Aesthetic disruption.
 Respirable dusts.

Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources
This concludes the
Chapter 15
Riches in Rock: Mineral Resources
LECTURE OUTLINE
earth
Portrait of a Planet
Third Edition
©2008 W. W. Norton & Company, Inc.
Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak
Chapter 15: Riches in Rock: Mineral Resources