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Chapter 3Chapter 3Minerals Minerals

The Building Blocks of The Building Blocks of RocksRocks

Changing Earth 5eChanging Earth 5e

Minerals OutlineMinerals Outline

1. What are minerals?1. What are minerals?2. Matter, atomic structure & chemical bonds2. Matter, atomic structure & chemical bonds3. World of minerals, crystals & composition 3. World of minerals, crystals & composition 4. Mineral groups & differences4. Mineral groups & differences5.5. GeoGeo--inSightinSight –– precious metalsprecious metals6.6. Physical properties Physical properties 7.7. GeoGeo--Focus: MicasFocus: Micas8.8. RockRock--forming mineralsforming minerals9. Minerals formation9. Minerals formation10.Natural resources 10.Natural resources


What are minerals?What are minerals?

Minerals Minerals are the are the building building blocks of blocks of rocks. rocks.

Introduction: MineralsIntroduction: Minerals


IntroductionIntroductionWhat is a mineral?

A mineral is

– Naturally – Inorganic– Crystalline solid– Characteristic physical properties– Specific chemical composition.

Gemstones – precious or semi-precious minerals or rocks used for decorative purposes

Fig. 3.1 a, p. 62


IntroductionIntroductionAre amber and pearls minerals?

– Amber is considered a semiprecious “stone,” but it is not a mineral because it is organic and not crystalline.

– Pearls, although they grow in mollusks, are minerals because they are crystalline and meet the other criteria for minerals.

Fig. 3.1 b-c, p. 62 Changing Earth 5eChanging Earth 5e

Matter Matter –– What is It?What is It?Atoms and Elements

– Matter: anything that occupies space & has mass (states/phases of matter: liquids, gases & solids)

– All matter is composed of chemical elements, which are themselves composed of atoms.

– Atoms consist of a nucleus, of protons and neutrons, and electrons that circle the nucleus.

– Elements are defined on the basis of the number of protons in the nucleus of an atom (i.e., the atomic number).

– Another characteristic of an atom is its atomic mass, the sum of the numbers of protons and neutrons in the nucleus.

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Atomic structure of matter: Atomic structure of matter:

Atoms consist of a:Atoms consist of a:

Nucleus of protons Nucleus of protons and neutrons and and neutrons and Electrons as a as a cloud of moving cloud of moving particles particles surrounding surrounding (spinning around) (spinning around) the nucleus.the nucleus.The (The (--) electrons ) electrons balance (+) protonsbalance (+) protons

Matter, atomic structure & chemical bondsMatter, atomic structure & chemical bonds


Matter Matter –– reviewreview

1. The number of protons in an atom’s nucleus determines its atomic number,

2. An atom’s atomic mass number is the total number of protons and neutrons in the nucleus. So, for example, if an atom has 6 protons and 8 neutrons its atomic number and mass numbers are 6 and 14, respectively.

Fig. 3.4, p. 64

Changing Earth 5eChanging Earth 5e Fig. 3-4, p. 64Stepped Art

6 p8 n

14C (Carbon 14)13C (Carbon 13)

6 p7 n

Nucleus

6 p6 n

12C (Carbon 12)

Isotope: some elements may have more or less neutrons than typical form, hence different in atomic mass. Some are radioactive (decay to other form).

Carbon: 12C (6p+6n)- typical, 14C (6p+8n)- radioactive



Bonding and Compounds

• Atoms are joined to one another by forces known as bonding.

• Atoms of different elements which are bonded to one another form compounds.

Fig. 3.5a, p. 65


Matter, atomic structure & chemical bondsMatter, atomic structure & chemical bondsBonding and CompoundsIonic Bonds - Ionic bonds transfer an electron, with opposite electrical charges attracting one another

Halite is a compound formed by the ionic bondingof sodium atoms to chlorine atoms. Note the atom sizes & arrangement (left) to form cubic crystals (right).

Fig. 3.5, p. 65 Changing Earth 5eChanging Earth 5e Fig. 3-5a, p. 65Stepped Art

Sodiumatom11 p+

11 e–

Sodiumion

11 p+

10 e–

+

Chlorineion

17 p+

18 e–

–

Chlorineatom17 p+

17 e–

electron transfer

Halite forms by transfer of sodium atoms electron to chlorine atom outer electron ring and resulting ionic attraction bonds the atoms together.

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Chlorideion

Sodiumion

Matter, atomic structure & chemical bondsMatter, atomic structure & chemical bondsionic bond & electron transfer in 3D

A negatively charged ion, is known as an anion. A positively-charged ion, is known as a cation


Sodium and chloride ionspack in a cubic structure.

Chlorideion

Sodiumion





Chlorideion

Sodiumion





Each cation is surrounded bysix anions, and vice versa.

Chlorideion

Sodiumion





Each cation is surrounded bysix anions, and vice versa.

Chlorideion

Sodiumion

NaCl crystal



Changing Earth 5eChanging Earth 5eTable salt, halite


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Electrical charges of atomic ionsElectrical charges of atomic ions

CationCation –– positively chargedpositively chargedAnion Anion –– negatively chargednegatively charged

Atomic ions arrange themselves Atomic ions arrange themselves according to charge and size.according to charge and size.

The cations of common mineral are small, while most anions are larger.



Crystalline structure are determined by how anions are arranged and how the cations fit between them.



Bonding and CompoundsCovalent Bonds – in covalent bonding the atoms share electrons in outer shell.

Can createvery strong mineral but depends on arrangementof bonds.

Example: Carbon bonds in Diamond vsGraphite Fig. 3.6, p. 66 Changing Earth 5eChanging Earth 5e

Matter, atomic structure & chemical bondsMatter, atomic structure & chemical bondsBonding and CompoundsCovalent Bonds – in covalent bonding the atoms share electrons.


Example: Carbon bonds in Diamond vsGraphite Fig. 3.6, p. 66


Matter, atomic structure & chemical bondsMatter, atomic structure & chemical bondsBonding and CompoundsCovalent Bonds – in covalent bonding the atoms share electrons in outer shell.


Example: Carbon bonds in Diamond vsGraphite Fig. 3.6, p. 66 Changing Earth 5eChanging Earth 5e


Bonding and Compounds

Metallic bonds– Metallic bonds result from extreme electron sharing.– Not common, primary metal minerals/ores

Van der Waals bonds– Van der Waals bonds are an extremely weak bond

without available electrons to form an attraction.– In graphite the sheets with covalent bonding are

held together by Van der Waals bonding

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World of MineralsWorld of Minerals

Mineral is composed of a naturally occurring inorganic substance

We define a mineral as naturally occurring– This excludes all synthetic substances made by

man like synthetic diamonds and rubies.

The term inorganic deserves special consideration– Animal and plant matter are not minerals– Certain organisms, however, do use minerals,

like calcite and quartz, to form their shells


World of MineralsWorld of MineralsCrystals: A mineral is a crystalline solid.

So why is it that not all mineral specimens show well-developed crystals?

As minerals form and grow, they may merge with one another to form a mosaic of interlocking crystalline solids that show no obvious crystals.

Nevertheless, individual minerals within this mosaic have their atoms arranged in a specific three-dimensional framework.

Fig. 3.8 a-b, p. 67

Smoky Quartz

Rose Quartz


Crystalline shape of the mineral is influenced by shape of individual crystal which starts the growth of mineral.

• With ideal conditions minerals can form perfect crystals.• Development of large crystal form is uncommon • Often find one or more faces/planes of the crystal form




Composition: A mineral has a specific chemical composition.

– By definition native elements are made up of only one chemical element, such as gold (Ag) and diamond (C).

– Most minerals are composed of two or more chemical elements, such as quartz (SiO²).

Geo-inSight 6., p. 73

Native Silver


Mineral Groups, CompositionMineral Groups, Composition

Fig. 3.10, p. 69

How many minerals are there?

There are thousands of known minerals, but commonly find only about 30 minerals on or near surface.

Most minerals can be grouped into 8 classes by chemical composition, with each class defined by anion charge.

The majority of minerals are composed of common elements.


Composition of the Crust

By volume ≈99% of the Earth's crust consists of only 8 elements:• OXYGEN—O• SILICON—Si• ALUMINUM—Al• IRON—Fe• CALCIUM—Ca• SODIUM—Na• POTASSIUM—K• MAGNESIUM—Mg

Mineral Groups, Composition Mineral Groups, Composition

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MineralMineral GroupsGroups, Composition , Composition

There are 92 naturally occurring elements, but only 8 are common in Earth’s crust.

Fig. 3.10, p. 69

Among the 8 elements,–Oxygen (47%) &

silicon (28%) aremost common in the crust.

–Most common minerals are madeup of oxygen, silicon, and one or more other elements.


Chemical classes of minerals (8 classes)• Silicates – contain O & Si (abundant)

(Olivine - MgSiO4) • Carbonates – contain C & O (anion CO3

2-) • Oxides - contain O & metallic cation

(Hematite - Fe2O3) • Sulfides - contain S & metallic cation

(Pyrite - FeS2)• Sulfates - contain SO4 & metallic cation

(Anhydrite CaSO4) • Halides – contain Cl, F, I, or Br

(Halite NaCl, Floride-CaF2)• Hydroxides – contain OH• Native elements – masses of all the same element

metallically bonded, gold & silver





Mineral GroupsMineral Groups

Table 3.1, p. 69

Most of the more than 3,500 known minerals are silicates(compounds of silicon and oxygen, and other elements).

Additional common mineral groups include

• carbonates, • oxides, • sulfides, • sulfates, & • halides.


Silicate ion (SiO44–)

Oxygen ions(O2–) Silicon ion

(Si4+)

Mineral Groups: Mineral Groups: silicate minerals6 Rock forming minerals: silicate minerals

Tetrahedra are the basic building blocks of all silicate minerals. About 95% of Earth’s minerals are silicates.




(Si4+)

The silicate ion forms tetrahedra.

Quartzstructure

Quartz is a silicate polymorph.

Mineral Groups:

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(Si4+)

The silicate ion forms tetrahedra.

Quartzstructure

Tetrahedra arranged in other ways are characteristic of other silicates minerals and determine their cleavage direction.

Mineral Groups:


Mineral GroupsMineral GroupsSilicate Minerals

– composed of the silica tetrahedra

Fig. 3.12, p. 70


Mineral Chemical formula

Cleavage planesand number of

cleavage directionsSilicate

structure Specimen

1 plane Isolatedtetrahedra

Olivine (Mg, Fe)2SiO4

Isolated tetrahedrons





structure Specimen


2 planes at 90°Single chains

Olivine

Pyroxene

(Mg, Fe)2SiO4

(Mg, Fe)SiO3

Single Chain Tetrahedrons





structure Specimen



2 planes at 60°and 120° Double chains

Olivine

Pyroxene

Amphibole

(Mg, Fe)2SiO4

(Mg, Fe)SiO3

Ca2(Mg, Fe)5Si8O22(OH)2

Double Chain TetrahedronsChanging Earth 5eChanging Earth 5e




structure Specimen




1 plane Sheets

Olivine

Pyroxene

Amphibole

Micas

(Mg, Fe)2SiO4

(Mg, Fe)SiO3


Muscovite:KAl2(AlSi3O10)(OH)2

Biotite:K(Mg, Fe)3AlSi3O10(OH)2

Continous Sheets Tetrahedrons

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structure Specimen




1 plane Sheets

Olivine

Pyroxene

Amphibole

Micas

Feldspars

2 planes at 90° Three-dimensionalframework

(Mg, Fe)2SiO4

(Mg, Fe)SiO3


Muscovite:KAl2(AlSi3O10)(OH)2

Biotite:K(Mg, Fe)3AlSi3O10(OH)2

Orthoclase feldspar:KAlSi3O8

Plagioclase feldspar: (Ca, Na) AlSi3O8

3-D Networks of Tetrahedrons


Mineral GroupsSilicate Minerals

– Ferromagnesian silicates - made up of iron, magnesium, or both combined with other elements.• dark in color and dense

Fig. 3.12 a, p. 70Fig. 3.13 a, p. 74


Mineral GroupsMineral GroupsSilicate Minerals

– Nonferromagnesian silicates - lack iron and magnesium• light colored

Fig. 3.11, p. 70Fig. 3.13 b, p. 74 Changing Earth 5eChanging Earth 5e

Mineral Groups Mineral Groups Carbonate Minerals

– All carbonate minerals have the carbonate radical (CO³)-²as in calcite (CaCO³) and dolomite [CaMg(CO³)²].

– Carbonate minerals are found mostly in the sedimentary rocks limestone and dolostone.

– Carbonates are derived from the shells and hard parts of marine organisms or are precipitated from seawater as evaporites.

Fig. 3.11, p. 70Fig. 3.14, p. 75


Mineral GroupsMineral GroupsOther Mineral Groups

– Native Elements

– All native elements are composed of a single element.

– Gold, copper and diamonds commonly occur as native elements.

Geo-inSight 6., p. 73 Changing Earth 5eChanging Earth 5e

Mineral GroupsMineral GroupsOther Mineral Groups

– Sulfides– All sulfide minerals contain sulfur plus a metallic

element as in galena (PbS) and pyrite (FeS²). – Sulfide minerals are found in all types of rocks.

They commonly form along mid-oceanic ridges

Fig. 3.14b, p. 75Fig. 3.15a, p. 78

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Mineral GroupsMineral Groups

Other Mineral Groups – Sulfates

– All sulfate minerals have the sulfate radical (SO4 -² ) as in gypsum (CaSO4 2H2O)

– Sulfate minerals are common in deserts, forming from evaporation of water

Fig. 3.11, p. 70 Changing Earth 5eChanging Earth 5e

Mineral composition and structure produce unique physical properties.

– Color

– Hardness

– Cleavage

– Crystal form

– Specific gravity

Physical Properties of MineralsPhysical Properties of Minerals

p. 60


Physical Properties of MineralsPhysical Properties of MineralsLuster and Color

– Luster is the quality and intensity of light reflected from a mineral and is characterized as metallic or nonmetallic.

– Color, in contrast, is a visual quality of minerals that results from the way they absorb or transmit light.

Fig. 3.15a, c, p. 78 Changing Earth 5eChanging Earth 5e

Physical Properties of MineralsPhysical Properties of MineralsCrystal Form

– Crystal form is useful for the identification of minerals that typically show well-developed crystals.

– For many other minerals, however, the crystals grow in proximity to form a crystalline mass, in which case other mineral properties such as luster, hardness, and cleavage must be used for identification.

Fig. 3.7, p. 67


Physical Properties of MineralsPhysical Properties of MineralsCleavage and Fracture

– Mineral cleavage refers to the breakage or splitting of mineral crystals along one or more smooth planes determined by atomic structure.

– When used with other mineral properties, cleavage can distinguish between minerals that otherwise look much the same.

– Fracture refers to the irregular breakage of a mineral Fig. 3.16, p. 79 Changing Earth 5eChanging Earth 5e Fig. 3-16, p. 79

Stepped Art

Cleavagein one direction

Cleavage plane Micas—biotiteand muscovite

Cleavage inthree directions,not at right angles

Calcite,dolomite

Cleavage insix directions

Sphalerite

Cleavage infour directions

Fluorite,diamond

Cleavage inthree directionsat right angles

Halite,galena

Cleavage intwo directionsat right angles

Potassiumfeldspars,plagioclasefeldspars

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HardnessMohs hardness scale

– Ten minerals are used to compare the hardness between all the rest.

Table 3.2, p. 79


Physical Properties of MineralsPhysical Properties of MineralsSpecific Gravity (Density) - The specific gravity is a way

to describe how heavy a mineral is.– Specific gravity is the ratio of the weight of a

mineral to an equal volume of water.– For example, galena has a specific gravity of 7.58 gm/cm3.

It is 7.58 times as heavy as an equal volume of water.

Fig. 3.14b-c, p. 75 Changing Earth 5eChanging Earth 5e


Other Useful Mineral Properties

– Feel - talc– Taste - halite– Magnetism - magnetite– Double refraction - calcite– React to dilute hydrochloric acid – calcite,

dolomite


RockRock--Forming MineralsForming MineralsHow do rock-forming mineralsdiffer from accessory minerals?

– A few minerals are common enough to be known as rock-forming minerals. Most of these are silicates.

– Accessory minerals can be ignored in this endeavor because they are present in minor quantities.

Table 3.3, p. 80 Changing Earth 5eChanging Earth 5e

RockRock--Forming MineralsForming MineralsCommon rock forming minerals

Fig. 3.19, p.80

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How Do Minerals Form?How Do Minerals Form?As molten rock material known as magma (lava at the

surface) cools, minerals begin to crystallize and grow– This determines the composition of various igneous rocks.

Fig. 3.19, p. 80 Changing Earth 5eChanging Earth 5e

Natural Resources and ReservesNatural Resources and Reserves

How does a resource differ from a reserve?

– A resource is any solid, liquid, or gaseous substance in rocks whose profitable extraction is potentially feasible. Many resources are concentrations of economically important minerals.

– A reserve is only that part of the resource base that can be extracted economically.



Fig. 3.20, p. 81

– While the United States is dependent on imports for many mineral resources, Canada is more self-reliant.



What factors affect the status or a resource?

– Market price is the most obvious determinate of whether a commodity is classified as a resource or reserve

– Other factors include geographic location, labor costs, and developments in science and technology.

End of End of MineralsMinerals

Chapter 3Chapter 3

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