Lecture OutlineLecture Outline

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Matter and its composition– Elements and atoms– Bonding and compounds

• Minerals

• Mineral groups– Silicates, Carbonates,…

• Physical properties of mineralsP.24

Matter and MineralsMatter and Minerals• Element – a pure

substance with unique chemical properties (on periodic table)

• Atoms – smallest particle of an element with that elements properties

Page 27

Matter and MineralsMatter and Minerals

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• All matter composed of atoms

• Atoms composed of:– Protons (1+) in nucleus

– (Total Number of Protons = Atomic Number)

– Neutrons (n) in nucleus (Protons+Neutrons = Mass)

– Electrons (1-) in orbit around the nucleus

Page 27

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

Page 28

Three Isotopes of CarbonThree Isotopes of Carbon

• Carbon-12– 6 protons– 6 neutrons– mass = 12

Carbon - Atomic Number 6

• Carbon-14– 6 protons– 8 neutrons– mass = 14

• Carbon-13– 6 protons– 7 neutrons– mass = 13

Periodic table, page 666-7

Atom combosAtom combos• compounds – a substance that contains 2 or more

different types of atoms– Molecule – the fundamental particle of a compound –

one unit. Like H2O molecule consists of 2 Hydrogrens & 1 oxygen atoms

• Mixture – a combination of 2 or more compounds not chemically united (salt and pepper – can easily separate)

• Ion – a charged “atom”– Positive ion = loss of electrons– Negative ion = gain of electrons

Bonding and CompoundsBonding and Compounds• Bonding joins atoms to other atoms

forming compounds (to make “happy”)• Three types:

– IONIC BONDING (metal + nonmetal)– COVALENT (sharing) BONDING

• (nonmetal + nonmetal)

– METALLIC BONDING (one metal with a sea of electrons)

Ionic Bonding -- Salt (NaCl)Ionic Bonding -- Salt (NaCl)• Sodium metal loses

an electron (-1) – becomes Na+1

a positive ion

• Chlorine (nonmetal) gains an electron (-1) – becomes Cl-1 a

negative ion

Sodium (Na+1)

Electron transfer

Chlorine (Cl-1)

Crystal structure of mineral NaCl, Halite

Want 8 electrons in the outer shell (octet rule)

Negative & positive ATTRACT !!

Covalent (Sharing) BondingCovalent (Sharing) Bonding

Adjacent atoms of carbon share electrons: Covalent bonding (in diamond)Strong bonds

Sheets of carbon atoms held together by weakVan der Waals bonds(graphite)

Share so 8 again

Mineral -- definitionMineral -- definition• Occurs naturally• Inorganic • Solid • Crystalline

– regular internal structure

• Narrowly defined chemical composition and physical properties (so if hard, always hard… etc)

Page 73 in book

Mineral -- importanceMineral -- importance

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Industrial societies depend on

– Glass, copper, gold, coal, gypsum, iron……..

• Gem minerals

– Diamonds, rubies, topaz…...

• Classification of rocks

– Based largely on mineral contents

The Naica Mine of Chihuahua, Mexico, is a working mine that is known for its extraordinary crystals. Naica is a lead, zinc and silver mine in which large voids have been found, containing crystals of selenite (gypsum) as large as 4 feet in diameter and 50 feet long. The chamber holding these crystals is known as the Crystal Cave of Giants, and is approximately 1000 feet down in the limestone host rock of the mine. The crystals were formed by hydrothermal fluids emanating from the magma chambers below. The cavern was discovered while the miners were drilling through the Naica fault, which they were worried would flood the mine. The Cave of Swords is another chamber in the Naica Mine, containing similar large crystals. http://www.crystalinks.com/mexicocrystals.html

Crystal formCrystal form

6 sides - Galena 12 sides - Garnet 8 sides - Diamond 6-sides - Quartz

Minerals are crystalline solids, can grow to perfect crystals with perfect facesunder ideal conditions (called euhedral)

Interfacial anglesInterfacial angles

Interfacial angles are constant for all crystals. Faces of Quartz form 120 degree angles – always if they have room to grow !

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7 Major Mineral Groupsdetermined by the type of chemical bonding

7 Major Mineral Groupsdetermined by the type of chemical bonding

1. Silicates - contain the Silicon-oxygen Tetrahedral (SiO4)-4

a. Ferromagnesian silicates (Fe+2 and Mg+2)

b. Non-ferromagnesian silicates

2. Carbonates - contain CO3 -2

– with either Ca +2, Mg +2, or both

7 Major Mineral Groupsdetermined by the type of chemical bonding

7 Major Mineral Groupsdetermined by the type of chemical bonding

3. Halides – Contains Cl -1 , F -1 , or Br -1 with a metal (like NaCl)

4. Sulfides – S -2 with a metal like lead or iron (PbS)

5. Oxides – O-2 with a metal like iron (Fe2O3)

(or even ice ! H2O)

4. Sulfates – SO4 -2 bonding with a metal (CaSO4)

5. Native elements like Gold & Silver !

Page 33

Importance of SilicatesImportance of Silicates

• Earth’s crust = 28% Silicon & 47% Oxygen (air is 78% Nitrogen & 21% oxygen)

• Silicates are most abundant minerals – 95% of Earth’s crust – Two thirds of all minerals are silicates

• Silica tetrahedra form strong bonds

• Therefore: Silicates are an important rock-forming mineral group!!

Silicate mineralsSilicate minerals

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Two major types of silicates:

• Ferromagnesian silicates -- rich in iron (Fe) and magnesium (Mg)

• Non-ferromagnesian silicates -- poor in iron and magnesium rich in silica

Page 32Silica Tetrahedron (SiO4)-4

Building blocks of silicate minerals --

silica tetrahedra

Page 33, fig. 2.10

Arrangements of TetrahedraArrangements of Tetrahedra

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

Olivine

Pyroxene

Amphibole

Micas

Quartz

Common Silicate MineralsCommon Silicate MineralsThe Light Silicates (non-ferromagnesian)

1. Feldspar Group – most common Pink (orthoclase) with Potassium (K+1) Dark to light (Plagioclase) with Ca +2 and Na +1

2. Quartz (SiO2) – clear unless it has inclusions (impurities)

3. Mica - Muscovite

Common Silicate MineralsCommon Silicate MineralsThe Dark Silicates (ferromagnesian)

1. Mica - Biotite

2. Amphibole

3. Pyroxene

4. Olivine

5. Garnet

Physical Properties of MineralsPhysical Properties of Minerals

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Color

• Streak

• Luster

• Cleavage

• Fracture

• Hardness

• Specific gravity (density)

• Crystal habit• Taste• Magnetism• Reaction to Acid• …….

Color Color

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Color is diagnostic for some minerals: Olivine is green, galena is silver-gray

• Color is important for metallic minerals

• Clear, colorless or transparent minerals have many color variations due to impurities and slight variations in chemical composition– Quartz may be colorless, white, pink, purple,

yellow, black, gray, etc.

StreakStreak

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Streak refers to the color of a powder mineral

• Produced by scraping the mineral against an unglazed ceramic plate.

Luster Luster

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Appearance of a fresh mineral surface in reflected light– Two types: metallic or nonmetallic

• Nonmetallic luster may be:– vitreous or glassy - the luster of glass (quartz)

– resinous - luster of resin (sphalerite)

– pearly - (talc)

– silky - (asbestos)

– dull or earthy - no luster (kaolinite)

– adamantine - brilliant (diamond)

Cleavage Cleavage

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Tendency of a mineral to break along parallel planes or directions of weakness in regular patterns-– One direction - micas

– Two directions - feldspar, pyroxene

– Three directions - halite, galena

– Four directions - fluorite– Six directions - sphalerite

Page 37

Fracture Fracture

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Mineral breakage along irregular surfaces

• Important in minerals without cleavage

• Occurs in minerals with bonding equally strong in all directions

Page 37Quartz with Conchoidal fracture

Hardness Hardness

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Resistance to being scratched• Related to Mohs Hardness Scale

– Diamond 10– Corundum 9– Topaz 8– Quartz 7– Orthoclase 6 Steel file (6.5)– Apatite 5 Glass (5.5- 6)– Fluorite 4– Calcite 3 Copper penny (3.0)– Gypsum 2 Fingernail (2.5)– Talc 1

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Crystal FormCrystal Form

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Manifestation of internal atomic arrangement

• All minerals are crystalline– microscopic crystals common

– large crystals rare

• Crystal form is characteristic of certain minerals– Quartz

– Fluorite

– Calcite

– Galena

Quartz

Calcite

Fluorite

Page 36

Carbonates, Sulfates, Sulfides, OxidesCarbonates, Sulfates, Sulfides, Oxides

Claude Spinosa© 1998 Wadsworh Publishing Company /ITP

• Carbonates contain the ion (CO3)-2

• (CO3)-2 can combine with

– Calcium (Ca) -- to form Calcite [CaCO3]

– or with Magnesium (Mg) -- to form Dolomite [Ca, Mg (CaCO3)2]

• Sulfates contain (SO4)-2 Gypsum

• Sulfides contain sulfur (S-2) Galena

• Oxides contain an element combined with Oxygen Hematite