MineralsChapter Chapter 2Earth 2Earth Materials—Materials—Minerals Minerals and Rocksand Rocks

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Earth Materials – Minerals

• Minerals are the basic units that make up most of Earth’s inorganic materials

• Minerals have many essential uses Can you name a few?

What is a mineral?

What is a mineral?

• 1. It is formed naturally

What is a mineral?

• 1. It is formed naturally

• 2. It has a crystalline structure

What is a mineral?

• 1. It is formed naturally

• 2. It has a crystalline structure

• 3. It is solid

What is a mineral?

• 1. It is formed naturally

• 2. It has a crystalline structure

• 3. It is solid

• 4. It has a narrowly defined chemical composition

What is a mineral?

• 1. It is formed naturally

• 2. It has a crystalline structure

• 3. It is solid

• 4. It has a narrowly defined chemical composition

• 5. It has characteristic physical properties

What is a mineral?• 1. It is formed naturally• 2. It has a crystalline structure• 3. It is solid• 4. It has a narrowly defined

chemical composition• 5. It has characteristic

physical properties• 6. It is inorganic

-- never living

Minerals

• Chemical composition: • composed of elements

Quartz – SiO2composed of one silicon atom and two oxygen atoms

• Distinct Properties: color, luster, hardness, breakage, streak, taste, odor, magnetic, surface features, reactive with acid

Matter and Its Composition

• Every substance on earth is composed of “matter”

• Matter has mass and volume – (occupies space)

solid, liquid, gascomposed of elements

• Elements are chemical substances• cannot be broken down chemically• composed of atoms

Atoms

• smallest particle that retains the nature of the element

Nucleus contains particles

protons: +neutrons: no charge

Electrons travel around the nucleus

electrons: --

Structure of an Atom

• The dense nucleus of an atom– consisting of

protons and neutrons

– is surrounded by a cloud of orbiting electrons

Particles in nucleus

• Atomic number: the number of protonsThis determines the name of the element.

• Atomic mass number is thenumber of protons + number of neutrons

The number of neutrons in an atom – may vary without changing the name of the

element

When neutrons vary• Isotopes of the same element are formed

Isotopes have the same atomic number• Isotopes have different atomic mass numbers• Isotopes of the same element behave the

same chemically• Isotopes are important in

radiometric dating

Carbon Isotopes

• Carbon atoms (with 6 protons) – have 6 neutrons = Carbon 12 (12C)– have 7 neutrons = Carbon 13 (13C)– or have 8 neutrons = Carbon 14 (14C)– thereby making up three isotopes of

carbon.

Bonding and Compounds• Bonding: atoms join to other atoms • Compound bonding of two or more

elements

• Oxygen gas (O2) is an element• Ice (H2O) is a compound•

Most minerals are compounds

Atomic Bonding

• Ionic bonds: electrons are donated or received

Atomic Bonding

• Common types of bonding among atoms to form minerals:

• Ionic bonds: electrons are donated or received

• Common types of bonding among atoms to form minerals:

• Ionic bonds: electrons are donated or received

• Covalent bonds: electrons are shared

Atomic Bonding

• Common types of bonding among atoms to form minerals:

• Ionic bonds: electrons are donated or received

• Covalent bonds: electrons are shared

• Metallic bonds: electrons are located in a “cloud” around nucleus

Atomic Bonding

• Common types of bonding among atoms to form minerals:

• Ionic bonds: electrons are donated or received

• Covalent bonds: electrons are shared• Metallic bonds: electrons are located in a

“cloud” around nucleus• Vanderwaals bonds: atoms are weakly

attracted

Atomic Bonding

Ionic Bonding• Ion: atom that has gained or lost one or

more electrons It has a negative or positive charge

• Ionic bonding – attraction between two ions of opposite

charge Goal: atoms are more stable when outer

electron shell is filled.

Ionic Bonding

halite

Covalent Bonding

• Covalent bonding– results from

sharing electrons

shared electrons

Metallic Bonding

Electrons are loosely arranged in a “cloud-like” arrangement.

Metals have properties of being good electrical conductors

Metals are malleable

Minerals—The Building Blocks of Rocks

Quartz: SiO2

Ratio: 1: 2

Quartz consists of 1 silicon atom for every 2 oxygen atoms

– Potassium Feldsparconsists of 1 potassium, 1 aluminum, and 3 silicon for every 8 oxygen atoms

KAlSi3O8

1: 1: 3: 8

Native Elements• consist of only one

element.• They are not

compounds.

gold – formula: Au

diamond – formula: C

Allotropes of carbon “polymorphs”

Mineral Properties• controlled by internal arrangement of

atoms– Chemical composition

– Crystalline structure

Colorhow reliable is color to identify a mineral?

Many varieties of quartz

Crystal form

If given enough room to grow freely– minerals form perfect crystals with – planar surfaces, called crystal faces– sharp corners– straight edges

Moh’s Scale of hardnessarranged from 1 to 10

• Hardness is a mineral’s resistance to abrasion or being scratched

Streak testcolor of a mineral in its powdered form

Breakage yes, they all break, but some break in

predictable patterns

• Irregular breakage or fracture:random, smooth, round (conchoidal) with no geometric shape or parallel flat sides

Breakage• Cleavage: • tendency to break in flat surfaces that are

parallel may have one, two, three, even four pairs of flat sides, or planes.

Types of mineral cleavage

Surface feature - feldspars

• Exsolution LamellaePotassium Feldspar

• StriationsPlagioclase Feldspar

Unique taste, odorhalite and sulfur

Reaction with dilute hydrochloric acid – carbonate minerals

Common rock forming minerals

Rock-Forming Minerals• Most rocks are solid aggregates of one or

more minerals

• Thousands of minerals occur in rocks, but most rocks have common rock-forming

minerals

Most rock-forming minerals are silicates,

but other groups are important

Silicates

• Silicates are minerals containing silica – Si and O

• They make up perhaps 95% of Earth’s crust– and account for about 1/3 of all known

minerals

• The basic building block of silicates – is the silicon oxygen tetrahedron

• which consists of one silicon atom• surrounded by four oxygen atoms

Earth’s crust:elements by weight %

Types of Silicates

• Silica tetrahedra can be – isolated units bonded to

other elements– arranged in chains (single

or double)– arranged in sheets– arranged in complex

3D networks

Types of Silicates

• Ferromagnesian silicates (dark)– contain iron (Fe), magnesium (Mg), or both

olivine, pyroxene, amphibole, biotite

• Nonferromagnesian silicates (light)contain potassium (K), sodium (Na), (Ca)calcium– Quartz, muscovite, feldspar

Ferromagnesian Silicates• Common ferromagnesian silicates include

Pyroxene-

amphibolebiotite

mica

olivine

Nonferromagnesian Silicates

Quartz Potassium feldspar

Plagioclase feldspar Muscovite

Other Mineral Groups

• Carbonates contain carbonate ion CO3 (CaCO3) calcite

Oxides (Fe2O3) MagnetiteHalides ( NaCl) HaliteSulfides (PbS) Galena