CHAPTER 4: Minerals. Making Steel This photo shows the process of making steel. What are some other products that we make from minerals?

CHAPTER 4:Minerals

Making Steel

This photo shows the process of making steel.

What are some other products that we make

from minerals?

Minerals

• A mineral is a naturally occurring, inorganic, crystalline solid with a definite, but sometimes variable, chemical composition.

Can you name any of these minerals?

Minerals continued

• Minerals are compounds that we use every day

• The average automobile contains:– more than 1000 kg of steel,– 110 kg of aluminum,– 23 kg of carbon,– 19 kg of copper,– 19 kg of silicon, – 10 kg of zinc, and – more than 30 other metals

including titanium, gold and platinum.

Common Minerals

Each mineral has unique chemistry and unique Crystalline Structure

Halite crystals from a salt shaker

Stev

en E

arle

Rocks and Minerals

• A Rock is a solid aggregate of minerals

Four different minerals are visible in this piece of granite. Can you name them?

Which metals or non-metals are mined in your province?

Mining/extraction/processingProcessing onlyFinancing/administration

Canadian mining & related activities

Identifying Minerals

• Geologists use Physical Properties to identify minerals• Identify by testing: cleavage, fracture, hardness, luster, colour,

streak, reaction to acid, crystal habit

Returning to the Halite model

• Fracture just means “breakage” (irregular or conchoidal)• Cleavage represents breaks along specific planes that are

determined by the mineral’s molecular structure

Hardness Tests

• Created in 1812 by Austrian mineralogist, Friedrich Mohs

Mineral Drag and DropAnimation

What is the hardness of a mineral that is soft enough to be scratched by a wire nail and hard enough to scratch a copper penny?

Luster, Colour and Streak

• Luster refers to the way a mineral reflects light.– (metallic, vitreous or “glassy”, silky, resinous, pearly, and earthy)

• Colour is not always a reliable property for identification of a mineral. – (Structure influences light absorption and reflection. Minor

impurities can have a significant influence on colour.)• Streak is the color of the powdered mineral.

– (testable by scraping the rock along a porcelain “streak plate”)

Atoms

• Atoms are the smallest components of nature with the properties of a given substance

Particle Mass Charge

Electron ~0 -1

Proton 1 +1

Neutron 1 0

Atomscontinued

For any given element:• Atomic number is the

number of protons in the nucleus

• Mass number is the total number of neutrons and protons in the nucleus

What are the atomic number and the mass number (a.k.a atomic weight) of the element carbon?

Isotopes

• Isotopes are atoms with differing numbers of neutrons (hence differing mass numbers) but a similar number of protons

Variations in Electrical Charge

• Variations in electrical charge form ions• Negative charge = anion• Positive charge = cation

When an atom loses electrons does it become a cation or an anion?

Octete Rule

• Atoms bond to achieve a stable electron configuration. Most atoms bond to achieve 8 electrons in the outer shell - the so-called “Octet Rule”

Ionic Bonding

• Minerals are compounds of atoms bonded together “… to achieve a stable electron configuration …”

In a sodium-chlorine ionic bond, which element is the anion and which is the cation?

Covalent Bonding

•“… to achieve a stable electron configuration …”

Metallic Bonding

• Bonding between atoms within metals. All “free” electrons sAhared in an “electron sea”.

• The metallic bonding in metals accounts for two of their important properties: – - they conduct electricity

(because electrons are free to move), and

– - they are malleable (because the bonds are flexible).

Native copper

Rocks and Minerals

• All types of rocks are primarily made up of minerals

• Igneous minerals crystallize from cooling magma, either slowly at depth or quickly at surface.

• Sedimentary minerals crystallize between sedimentary grains from dissolved elements in groundwater, usually in the absence of oxygen.

• Metamorphic minerals recrystallize from existing minerals where conditions in the crust cause high heat and pressure.

Formation of Magma

• Magma forms in three major tectonic settings

submarine volcanism

Oxygen and Silicon are the two most abundant elements in the crust

Silica

• Silica - 4 oxygen atoms surround a single silicon atom. Each oxygen atom covalently shares 1 electron with the silicon atom, jointly filling its outermost shell.

Shield volcano

Composite volcano

Hot spot

Count the charges. What is the overall charge on a silica tetrahedron?

Types of Silicate Structures

Where silica tetrahedra are joined together O atoms are shared, and the overall negative charge is reduced.

Metallic Cations

• Metallic cations join silicate structures together to form a neutral compound

• Cations of like size and charge substitute within silicate structures.

• This forms a wide variety of minerals• Most commonly substituted Cation pairs

are Na+/Ca2+, Al3+ /Si4+, and Fe2+/Mg2+• Olivine varies by Single Cation Substitution

(e.g., Fe for Mg)• Plagioclase Feldspar varies by Double

Cation Substitution (meaning that when Ca substitutes for Na, Al substitutes for Si)

Common Silicate Minerals

What exactly is meant by the notation (Fe,Mg)

or (Ca,Na)?

Seven Common Rock-Forming Minerals

Mt. Pinatubo, 1991

Olivine

PyroxeneBiotite

Quartz

Calcite

Plagioclase and Orthoclase

All but one of these are silicate minerals. Which

one is not a silicate?

Amphibole

The Feldspar group

Bingham Canyon Mine (Utah)Olivine crystals (light green) and fragments of basalt (black) from Green Sand Beach, Hawaii

Steven Earle

7 Major Classes of Minerals

Silicates Native Elements

Sulfides

Halides

Carbonates

Feldspar – NaAlSi3O8

Pyrite - FeS2

Fluorite – CaF2

Hematite – Fe2O3

Native copper - Cu

Gypsum - CaSO4·2H2O SulfatesCalcite – CaCO3

Oxides

Mining

• Mining is an important part of our current economic and industrial systems.

• The potential for environ-mental damage is real, but it can be minimized.

• By law, mining plans must include stream, ground-water and topsoil protection, careful waste rock handling, prevention of acid rock drainage, erosion, sediment, and dust control and restoration of the shape of the land.

Acid Rock Drainage destroys streams near many mines

Acidic drainage at the Mt. Washington Mine, on Vancouver Island, BC

Stev

en E

arle

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