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Lecture Outlines PowerPoint

Chapter 2

Earth Science 11e

Tarbuck/Lutgens

Earth Science, 11e

Minerals: Building Blocks of Rocks

Chapter 2

Minerals are essential:• They’re every manufactured product• They’re essential to good health• Knowledge of minerals enables us to understand

earth processes

Minerals: the building blocks of rocks

Definition of a mineral: What are the 5 characteristics that make a mineral?

•Natural (found in nature)

•Have a definite chemical composition (chemical formula)

•Possess an orderly internal structure of atoms

(A.K.A. crystal structure)

•Solid

•Inorganic (never living)

Mineraloid - lacks an orderly internal structure

Composition and structure of minerals

Elements • Basic building blocks of minerals • Over 100 are known

What is the #1 most abundant element in the Earth’s crust?????

AtomsSmallest particles of matter Have all the characteristics of an element

Composition of continental crust

Figure 2.16

Periodic table of the Elements

Figure 2.4

Simplified view of the atom

Figure 2.5

How atoms are constructed

__________ central part of an atom that contains • ___________ positive electrical charges • ___________ neutral electrical charges

Energy levels, or shells • Surround nucleus • Contain __________ negative electrical

charges

Nucleus

Protons

Neutrons

electrons

How atoms are constructed

_______ _________ is the number of protons in an atom's nucleus

Bonding of atoms • Forms a compound with two or more elements

• Ionic bonds and metalic bonds

• _______are atoms that gain or lose electrons

___________ Have varying number of neutrons and are radioactive

Atomic number

Ions

Isotopes

How atoms are constructed

Isotopes • Have different mass numbers – the sum of the

neutrons plus protons • Many isotopes are radioactive and emit energy

and particles

How minerals form:

1. Underground in the magma process (most minerals)

2. Re-form deep within the earth in the pressure process.

3. Near the surface in the evaporation (of water) process

How Minerals form • The Magma Process:

1. Molten (liquid) rock in a magma chamberAt, near or under earth’s surface, rises

2. The magma begins to cool and atoms, ions and molecules form various mineral compounds.

3. The molecules of the compounds mass together to form crystals.

The Pressure Process:1. Rock is exposed to high pressures and temperatures, and the

minerals begin to break down.

2. As pressure and temperature continue, the molecules RE-FORM into new minerals.

3. The minerals are elongated in shape due to the pressure.

The Evaporation Process:

1. Ions (such as salt or calcium) are dissolved in water.

2. The water evaporates, and the ions form minerals

such as halite and calcite.

• Examples: halite (NaCl salt)» limestone (calcite)

Minerals

Physical properties of minerals • Crystal form• Luster• Color• Streak• Hardness• Cleavage

The mineral quartz often exhibits good crystal form

Factors that determine crystal formation:

1. Time

2. Space

3. Evaporation Rate

4. Dissolved Materials

5. Temperature

6. Pressure Largest uncut diamond found in the Letseng Mine in southern Africa. A near-flawless white gem weighing nearly 500 carats. It was discovered on Sept. 8, 2008 It weighs 478 carats, with very few inclusions and of outstanding color and clarity.

Mexico's Cueva de los Cristales (Cave of Crystals) contains some of the world's largest known natural crystals—translucent beams of gypsum as long as 36 feet (11 meters). Volcanic activity that began about 26 million years ago created Naica mountain and filled it with high-temperature anhydrite gypsum. When magma underneath the mountain cooled and the temperature dropped, the anhydrite began to dissolve and for millions of years have been deposited in the caves in the form of huge selenite gypsum crystals.

1. TIME and mineral formation

The RATE at which the molten magma cools determines the crystal size.

• If the magma has a lot of time and it cools s-l-o-w-l-y then the crystals will….

* (example: granite)

LARGE and well-formed

• If the magma cools quickly, then the crystals will….

*example: obsidian has a glass-like structure

Small / microscopic / not well-formed

Classzone Internet Investigation ES0506

“How Do Crystals Grow?”

2. Space

3. Evaporation rate

3. Amount of dissolved materials

3. Temperature

4. Pressurehttp://www.classzone.com/books/earth_science/terc/content/investigations/es0506/

Summarize in a sentence:

So…. To grow the biggest, best synthetic diamond crystal, you would….

time,

space,

cooling rate (temperature)

pressure

Pyrite (fool’s gold) displays metallic luster

Figure 2.10

Figure 2.12

Mohs scale of hardness

Minerals

Physical properties of minerals • Fracture• Specific gravity• Other properties

• Taste

• Smell

• Elasticity

• Malleability

Minerals

Physical properties of minerals • Other properties

• Feel

• Magnetism

• Double Refraction

• Reaction to hydrochloric acid

• Fluorescence (UV)

Some rocks and minerals “glow” under UV (black) light

Minerals A few dozen minerals are called the rock-forming

minerals • The eight elements that compose most rock-forming

minerals are…• OXYGEN (O) (46.6% by weight)• SILICON (Si), (27.7% by weight) • aluminum (Al), • iron (Fe), • calcium (Ca), • sodium (Na), • potassium (K), and • magnesium (Mg)

Composition of continental crust

Figure 2.16

??????

How can it be that… oxygen (a gas) and

silicon (a metalloid) are

the #1 and #2 most abundant elements in the earth’s crust?

Minerals Mineral groups

• Most common Rock-forming mineral group is the:

Silicates

• Contain the silicon-oxygen tetrahedron (molecule)

• Four oxygen atoms surrounding a much smaller silicon atom

Silicon-oxygen tetrahedron(SiO4)-4 molecule

Figure 2.17

Minerals

Mineral groups • Rock-forming silicates

• Combines with other atoms to form the various silicate structures

• Groups based upon tetrahedral arrangement • Olivine – independent tetrahedra • Pyroxene group – tetrahedra are arranged in

chains• Amphibole group – tetrahedra are arranged in

double chains

Minerals

Mineral groups • Rock-forming silicates

• Groups based upon tetrahedral arrangement

• Micas – tetrahedra are arranged in sheets

• Two types of mica are biotite (dark) and muscovite (light)

• Feldspars - Three-dimensional network of tetrahedra

Hornblende – a member of the amphibole group

Minerals

Mineral groups • Rock-forming silicates

• Groups based upon tetrahedral arrangement

• Feldspars

• Two types of feldspar are Orthoclase and Plagioclase

• Quartz – three-dimensional network of tetrahedra

Three examples of perfect cleavage – fluorite, halite,

and calcite

Conchoidal fracture

Figure 2.15

Potassium feldspar

Plagioclase feldspar

Minerals

Mineral groups • Rock-forming silicates

• Feldspars are the most plentiful mineral group

• Crystallize from molten material

• Nonsilicate minerals • Major groups

• Oxides• Sulfides

Minerals

Mineral groups • Nonsilicate minerals

• Major groups

• Sulfates

• Carbonates• “Native” elements

Native Copper

Minerals

Mineral groups • Nonsilicate minerals

• Carbonates

• A major rock-forming group

• Found in the rocks limestone and marble

• Halite and gypsum are found in sedimentary rocks

• Many have economic value

Minerals

Mineral resources • Reserves are already identified deposits• Ores are useful metallic minerals that can be

mined at a profit • Economic factors may change and influence a

resource

An underground halite (salt) mine

Mineral Gemstones

• A gemstone is defined as…

Precious? semi-precious?

Tumbled “Gems” Stones

Gems are valued for their reflective properties due to the way they cut (facets).

Topaz

• Rough – uncut – unpolished

Malachite

• Raw form cut and polished

Turquoise

• Natural turquoise jewelry

Opal

• Raw form

End of Chapter 2