Chapter 5 Atoms, Elements, and Minerals

The next few chapters in geology are mostly about rocks. Nearly all rocks are made of minerals, so in order to learn about rocks you need to know something about minerals. In Chapter 5, you will discover that:

1. Each mineral is made up of specific chemical elements, the atoms of which are organized in a special arrangement.

2. The chemical makeup and its internal structure determine an element’s physical properties.

3. A mineral can be identified by its physical

characteristics, such as: cleavage, crystal form, fracture, hardness, lustre, colour, streak, and specific gravity.

What is Matter?

• Matter – the substance of which any physical object is composed. Everything is made of matter.

States of Matter:• Solid • Liquid• Gas

Controlling factors:• Temperature• Pressure

Examples: Gold Mercury Oxygen

solid liquid gas

The stuff that makes up all matter

• The make-up of solid matter on Earth:Atoms Elements Compounds Minerals Rocks

(smallest) (largest)

What is an atom?

An atom is the smallest particle of a matter that keeps the properties of that matter. For example, all sodium atoms are essentially identical to all other sodium atoms. Water (H2O) can be broken down into two atoms of hydrogen (H) and one atom of oxygen (O).

What are elements?

Elements are the fundamental building blocks of matter. Elements cannot be broken down into smaller units. Elements are pure substances and are made of one or more of the same type of atoms. All elements are listed in the periodic table of the elements.

Periodic Table of Elements

Element abundances in the crust

All others: 1.5%

What are the most abundant elements in the Earth’s crust?

1. Oxygen (O)

-Oxygen is the most abundant element in the crust (makes up about 50% of the crust)

-Oxygen bonds easily with other elements

2. Silicon (Si)

-Most silicon form bonds with oxygen to form silica

-Quartz (SiO2) is pure silica that has been crystalized

-Any mineral that contains silica is called a silicate

3. Aluminum (Al)

-Aluminum is more common that iron, but difficult to separate from rocks because it binds very tightly with oxygen.

Other elements in the Top 8 include:

Iron Potassium

Calcium Magnesium

Sodium

Mineral characteristics

• Definition of a Mineral:1. naturally occurring

2. inorganic

3. solid

4. characteristic crystalline structure

5. definite chemical composition

steel plastic sugar table salt mercury ice coal

basalt obsidian mica gold paper chalk coral

no, #1 no, #1 no, #1,2 YES! no, #3 YES! no, #2

no, #5 no, #4 YES! YES! no, #1,2 no, #2 no, #2

QUIZ!!!

Mineral characteristics

• Naturally formed– No substance created artificially is a mineral. examples: plastic, steel, sugar, paper

• Inorganic– Anything formed by a living organism and

containing organic materials is not a mineral. examples: wood, plants, shells, coal

• Solid– Liquids and gases are not minerals. examples: water, petroleum, lava, oxygen

Mineral characteristics

• Characteristic crystalline structure– must have an ordered arrangement of atoms– displays repetitive geometric patterns in 3-D

glass not a mineral (no internal crystalline structure)

• Definite chemical composition– must have consistent chemical formulaexamples: gold (Au), quartz (SiO2), orthoclase (KAlSi3O8)

basalt (like many other rocks) contains variable ratios of different minerals; thus, has no consistent formula

– Only ~30 occur commonly (whew!)

– Why not more?• Some combinations are chemically impossible

• Relative abundances of elements don’t allow more

How many minerals are there?

• Nearly 4,000 types of minerals

Silicates• Most minerals are silicates (which

means they contain silicon & oxygen)• Silicates have a very special structure

called a tetrahedron. This tetrahedron is the building block of a the silicate crystals

Silicate tetrahedrons can combine together to make much bigger structures.

Diamond is NOT a silicate, but pure crystallized carbon. It is a very strong tetrahedron (and also a mineral).

Minerals of the Earth’s CrustThe following are silicate minerals. They

are the most common minerals and make up about 90% of the crust.

1. Feldspars

2. Quartz

3. Pyroxenes

4. Amphiboles

5. Micas

FeldsparPyroxeneQuartz

Amphibole Mica

Other common mineral crystals include:1. Clay minerals (which is another group of silicates)

2. Non-silicates

Example: gypsum Example: calcite

Less common minerals of commercial value:

1. Halite (salt)

2. Diamond

3. Gold

4. Hematite & magnetite (iron)

5. Chalcopyrite (copper)

Physical Properties of Minerals

1. Colour

2. Streak

3. Lustre

4. Hardness

5. External crystal

6. Cleavage (most important)

7. Fracture

8. Specific gravity

Class Activity

1.Briefly explain each of the physical properties of minerals.

Refer to Properties of Minerals

2. ID some minerals (Resource)

Video

Quiz

1. Most common element in the crust.

2. Most common mineral.

3. Which one (or ones) is/are a mineral?Plastic quartz salt

4. What is geology?

5. What is the topic of your geology project?