Chapter 9 Section 1. Learning Objectives Identify the difference between a mineral and a rock Describe the properties that are used to identify minerals.

Chapter 9Section 1

Minerals

Learning Objectives

• Identify the difference between a mineral and a rock

• Describe the properties that are used to identify minerals

• Each mineral has a set of physical properties that can be used to identify it

New Vocabulary

• Mineral• Rock• Crystal • Gem• Ore

What is a mineral?• Where are they found?• Are they in a cave? Or in a

mine?• Minerals can be found

anywhere and everywhere!• What are some examples of

minerals?– Pencils (graphite), salt, metal

pots, glassware, ceramic dishes

What is a Mineral?

• Minerals: inorganic, solid materials found in nature

• Inorganic: usually not formed by plants or animals

• Minerals often have a beautiful crystal shape• The particular chemical makeup and

arrangement of the atoms in the crystal is unique to each mineral

• Rocks: usually made of two or more minerals

Minerals

• Each mineral has a unique characteristics that is used to identify it

• Over 4,000 minerals have been identified so far

How do minerals form?• There are several ways

minerals form:

1. Melted rock material in Earth (Magma)

• As it cools, atoms combine in orderly patterns to form minerals

• Also form as magma reaches Earth’s surface (lava)

How do Minerals form?

2. Evaporation forms minerals– Salt crystals appear when seawater evaporates;

other dissolved minerals can crystallize

3. Precipitation can form minerals– Water can hold only so much dissolved material– Extra separates and falls out as solid

To figure out how a mineral was formed, you have to look at the size of the mineral crystal and how the crystals fit together

Properties of Minerals• Each mineral has a set of physical

properties than can be used to identify it• We will discuss 6 properties of minerals

that are helpful in identifying them

1. Crystals: solid materials that have a repeating pattern of atoms– Pyrite commonly forms crystals with 6 faces

Properties of Minerals

2. Cleavage and Fracture• The way a mineral breaks can help identify it• Splits into pieces with smooth, regular panes

that reflect light = cleavage• Minerals that break into pieces that are

jagged or have rough edges = fracture

Properties of Minerals

3. Color: • Sometimes a minerals color can help figure

out what it is• Color can also fool you! (Fool’s gold is pyrite)• The same mineral can occur in a variety of

colors– Calcite in figure 5 pg 271

Properties of Minerals

4. Streak & Luster• Streak: The color of the powered form of a mineral• If a mineral is rubbed across an unglazed, white tile,

(streak plate) it produces a streak of color• Sometimes the streak is different than the color of the

mineral• Luster: describes how light reflects off the mineral’s

surface– Is it shiny, dull, pearly, glassy, or earthy

• Metallic minerals = shiny like a metal• Nonmetallic minerals = pearly, glassy, dull or earthy

Properties of Minerals

5. Hardness• Some minerals are harder than others• Soft ones like talc can be scratched with

fingernails• Hard ones like diamonds are so hard they can

be used to cut almost anything else• Mohs scale: classifies minerals on a scale of 1

(softest) to 10(hardest)– Use one mineral to scratch another to see which

on is harder

Properties of Minerals

6. Specific Gravity• Some minerals are heavier than others• Specific gravity compares the weight of a

mineral with the weight of an equal volume of water

– Fool’s gold is 5 times heavier than water; real gold is 19 times heavier than water

– Easily tell this by holding each in your hand

Other Properties

• There are other properties that can help identify minerals– Magnetite will attract to a magnet– Calcite will fizz when it comes into contact with

acids– Some scientists will taste minerals to identify them

(YUCK!!)

Common Minerals

• There are over 4,000 minerals that make up most rocks– “rock-forming minerals”

• Most rock-forming minerals are silicates– They contain the elements silicon and oxygen– Quartz is pure silica

• Feldspar (type of silicate mineral) makes up ½ rocks • Carbonates are another type of important rock-

forming minerals– Made of carbon and oxygen– Calcite is a carbonate

Common Minerals

• Other common minerals can be found in rocks that formed at the bottom of ancient seas as they evaporated– Gypsum is abundant in many places– Halite or rock salt is found in large quantities in

the Midwest

Gems

• Gems are minerals that are rare and can be cut and polished

• Must be clear with few or no blemishes or cracks

• Must have beautiful luster or color• Very few minerals meet these standards• Gems are very rare and valuable

Making A Gem

• Gems are rare because they are formed under special conditions

• Diamonds are forms of the element carbon• Diamonds can be made in a lab setting or they

are formed deep within Earth’s mantle• Volcanic eruptions bring diamonds to the

surface for miners to find• Pg 274 figure 9

Ores

• A mineral is called an ore if it contains enough of a useful substance that it can be sold for profit

• Many metals that we use come from ores– Iron used to make steel– Lead used to make batteries– Magnesium in vitamins

• Extracted from Earth’s surface by mining

Conserving Ores

• Scrap metal recycled or reused to decrease mining

• Ores take millions of years to form so they are considered a non-renewable resource

• Mining can disrupt environments, landscapes, use valuable resources and increase production costs

Ore Processing• After mining, ore must be processed to extract

the desired mineral or element• Copper goes through a process called smelting• After this process, copper can be refined or

purified• Then it can be processed into many materials– Sheet metal, electrical wiring, cookware, etc…

Review Questions

1. Explain the difference between a mineral and a rock. What are 5 common rock-forming minerals? (pg 273 for minerals that form rocks)

2. List 5 properties that are commonly used to identify minerals.

3. Describe an event that must occur in order for diamond to reach Earth’s surface. Where in Earth is diamond formed?

4. Would you want to live close to a gold mine? Explain why or why not.