Lecture 5

Question 1

The most abundant chemical elements in the continental crust

Answer 1

Dominantly oxygen and silicon

Question 2

Differentiation process causes _____ elements to sink to the core, while _____ elements such as ________ and _______ , stay near the crust

Answer 2

Heavier
Lighter
Oxygen and silicon

Question 3

First column of periodic table

Answer 3

Form bonds with silicon so enhanced concentration of these elements found at the crust

Question 4

Radiogenic isotopes

Answer 4

• radioactive and decay at known rates
• unstable
• used for radiometric dating

Question 5

Radiogenic coupling example

Answer 5

87Rb (unstable) to 87 Sr (stable)

Question 6

By 1 half life the parent and daughter atoms are

Answer 6

50:50

Have equal concentrations

Question 7

What time of bonding is found in most minerals

Answer 7

Ionic bonding

Question 8

Structure of diamond versus structure of graphite

Answer 8

• both covalent bonding
• diamond has strong bonds whereas graphite (forms sheet bonds) which are weaker
• same chemical composition; only differ in their framework

Question 9

Bonding in solids typically produces a __________

Answer 9

Crystal lattice

Question 10

Definition of a crystal

Answer 10

Regular arrangement of atoms (crystal lattice)

This arrangement is responsible for many mineral properties

Question 11

Minerals are a __________ of crystals

Answer 11

Subset

All minerals are crystals but not all crystals are minerals

Question 12

Four criteria for a crystal to be called a mineral

Answer 12

1. Naturally occurring
2. Solid
3. Specific chemical composition or range of compositions (I.e.., constant composition that can’t change into something else)
4. Repeating atomic configuration-crystal structure or crystalline

Question 13

A rock is

Answer 13

A mixture of minerals

Question 14

Most common type of mineral in Earth’s crust

Answer 14

• silicate anion or the tetrahedron (SiO4)4-

- combination of Si4+ with 4 O2-

Question 15

Minor minerals

Answer 15

Oxides
Carbonates
Sulfides
Native elements
Sulphates
Phosphates

Question 16

The silicate anions can be found as

Answer 16

Isolated tetrahedra

Polymerize into pairs, rings, sheets, chains, or frameworks

Question 17

Isolated tetrahedra

Answer 17

• single tetrahedron
• olivine (Mg2SiO4)
• cleavage: none

Held together by ionic bonds

Question 18

Single chain silicate

Answer 18

• single chain
• pyroxene group CaMg(SiO4)2 (variety: diopside)
• cleavage: two directions at 90 degrees

Question 19

Double chain silicates

Answer 19

• double chain
• Amphibole group Ca2Mg5(Si4O11)2(OH)2 (variety: tremolite)
• cleavage: two directions at 120 degrees

Question 20

Sheet silicates

Answer 20

• Mica
• forms a sheets
• cleavage: one direction

Question 21

Framework silicates

Answer 21

Feldspar:

• 3D network
• cleavage: two directions at 90 degrees

Quartz:

• undisturbed pure network
• cleavage: none

Question 22

What are the most abundant minerals in the continental crust

Answer 22

Silicates (95% of all minerals in the crust)

Question 23

Mineralogy of Earth’s mantle

Answer 23

Upper: dominantly silicates

Lower: silicates and oxides

Question 24

What are the most common types of silicates in the earth’s crust

Answer 24

Feldspar at 60%

Quartz at 15%

Reminding 20% are other forms of silicates (5% non silicates)