Chapter 3 Section 1 Mrs. Hutson

The Big Idea

Minerals have characteristic physical and chemical properties that determine how each mineral is used by humans.

The white substance on these rocks may look like cotton candy, but the substance is actually the mineral epsomite. Epsomite is a sulfite mineral that can form in caves. Epsomite crystals can appear needlelike, hairlike, or cottonlike. This sample of epsomite is from Ellison’s Cave in Georgia.

What Is a Mineral? You may think that all minerals look like gems. But, in fact, most minerals look more like rocks.

Does this mean that minerals are the same as rocks? Well, not really. So, what’s the difference?

For one thing, rocks are made of minerals, but minerals are not made of rocks. A mineral is a naturally formed, inorganic solid that has a definite crystalline structure.

Mineral Structure

By answering the four questions, you can tell whether an object is a mineral.

If you cannot answer “yes” to all four questions, you don’t have a mineral. Three of the four questions may be easy to answer.

The question about crystalline structure may be more difficult.

4 questions Is it a nonliving material? Is it a solid? Is it found in nature? Does it have a crystalline structure?

Does it have the same chemical composition throughout?

Does it contain one or more of any element

Atoms and Compounds

Each element is made of only one kind of atom.

An atom is the smallest part of an element that has all the properties of that element.

Like other substances, minerals are made up of atoms of one or more elements

Most minerals are made of compounds of several different elements.

A compound is a substance made of two or more elements that have been chemically joined, or bonded.

A mineral that is composed of only one element is called a native element.

Sodium

Crystals Solid, geometric forms of minerals

produced by a repeating pattern of atoms or molecules that is present throughout the mineral are called crystals.

A crystal’s shape is determined by the arrangement of the atoms or molecules within the crystal.

Watch “Crystals” by Brainpop…

1.What element are diamonds made from?

2. What do all crystals have in common?

Crystals Continued The arrangement of atoms or molecules

in turn is determined by the kinds of atoms or molecules that make up the mineral.

Each mineral has a definite crystalline structure. All minerals can be grouped into crystal classes according to the kinds of crystals they form

How do minerals form?

1) Cooling of magma (hot, liquid rock and minerals inside the earth (from the mantle)) Fast Cooling = No Crystals (mineraloids) Medium Cooling = small crystals Slow Cooling = large crystals

How do minerals form?

2) Elements dissolved in liquids (usually water)

Two Groups of Minerals

Silicate Minerals Silicon and oxygen are the two most

common elements in the Earth’s crust. Minerals that contain a combination of these two elements are called silicate minerals.

Silicate minerals make up more than 90% of the Earth’s crust. The rest of the Earth’s crust is made up of nonsilicate minerals.

Mineral Group Characteristics Examples

Silicates

Contain oxygen & silicaThe most abundant group of minerals

Quartz, mica

MICA Quartz

Nonsilicate Minerals

Minerals that do not contain a combination of the elements silicon and oxygen form a group called the nonsilicate minerals.

Some of these minerals are made up of elements such as carbon, oxygen, fluorine, and sulfur.

Mineral Group Characteristics Examples

Non-Silicates

Make up only 5% of the Earth’s crustInclude some of the most important minerals

iron, copper, gold, silver, diamonds, rubies

Silver

GoldRuby Iron

Copper

Diamond

Chapter 3Section 2Mrs. Hutson

Identifying Minerals

If you closed your eyes and tasted different foods, you could probably determine what the foods are by noting properties such as saltiness or sweetness.

You can also determine the identity of a mineral by noting different properties.

What You Will Learn

Identify seven ways to determine the identity of minerals.

Explain special properties of minerals.

Color The same mineral can come in a variety of colors. For example, in its purest state quartz is clear.

Samples of quartz that contain various types of and various amounts of impurities, however, can be a variety of colors.

Color Besides impurities, other factors can change the

appearance of minerals. The mineral pyrite, often called fool’s gold,

normally has a golden color. But if pyrite is exposed to air and water for a long period, it can turn brown or black.

Because of factors such as impurities, color usually is not the best way to identify a mineral.

Luster The way a surface reflects light is called

luster. When you say an object is shiny or dull, you

are describing its luster. Minerals have metallic, submetallic, or

nonmetallic luster. If a mineral is shiny, it has a metallic luster. If the mineral is dull, its luster is either

submetallic or nonmetallic.

Different Types of Luster

Streak The color of a mineral in powdered form

is called the mineral’s streak. A mineral’s streak can be found by

rubbing the mineral against a piece of unglazed porcelain called a streak plate.

The mark left on the streak plate is the streak.

Minerals must be softer than the streak plate.

The streak is a thin layer of powdered mineral. The color of a mineral’s streak is not always the

same as the color of the mineral sample. Unlike the surface of a mineral sample, the

streak is not affected by air or water. For this reason, using streak is more reliable

than using color in identifying a mineral.

Streak…can help identify quartz

http://www.childrensmuseum.org/geomysteries/cube/b3.html

Cleavage and Fracture

Different types of minerals break in different ways. The way a mineral breaks is determined by the arrangement of its atoms.

Cleavage is the tendency of some minerals to break along smooth, flat surfaces.

Fracture is the tendency of some minerals to break unevenly along curved or irregular surfaces.

Clevage

Fracture

Cleavage or Fracture?1.

4.

3.

2.

Hardness A mineral’s resistance

to being scratched is called hardness.

To determine the hardness of minerals, scientists use Mohs hardness scale, shown in Figure 5.

Notice that talc has a rating of 1 and diamond has a rating of 10.

Hardness (continued) The greater a mineral’s resistance to being

scratched is, the higher the mineral’s rating is.

To identify a mineral by using Mohs scale, try to scratch the surface of a mineral with the edge of one of the 10 reference minerals.

If the reference mineral scratches your mineral, the reference mineral is harder than your mineral.

Density Density is the measure of how much

matter is in a given amount of space. In other words, density is a ratio of an object’s mass to its volume

The ratio of an object’s density to the density of water is called the object’s specific gravity.

Special Properties

Some properties are particular to only a few types of minerals.

The properties shown in Figure 6 can help you quickly identify the minerals shown.

To identify some properties, however, you will need specialized equipment.

Watch Brainpop—“Mineral Identification”

1. If a mineral can scratch your fingernail, the mineral is _______________ than your fingernail.

2. What is luster?

Chapter 3 Section 3Mrs. Hutson

The Formation, Mining, and Use of MineralsWhat You Will Learn Describe the environments in which

minerals form. Compare the two types of mining. Describe two ways to reduce the effects

of mining. Describe different uses for metallic and

nonmetallic minerals.

Minerals and Environments Minerals form in a variety of environments in

the Earth’s crust. Each of these environments has a different

set of physical and chemical conditions. Therefore, the environment in which a mineral

forms determines the mineral’s properties. Environments in which minerals form may be

on or near the Earth’s surface or deep beneath the Earth’s surface.

Mining Many kinds of rocks and minerals must

be mined to extract the valuable elements they contain.

Geologists use the term ore to describe a mineral deposit large enough and pure enough to be mined for profit.

Mining Continued Rocks and minerals are removed from

the ground by one of two methods Surface mining or subsurface mining

The method miners choose depends on how close to the surface or how far down in the Earth the mineral is located.

Surface Mining

When mineral deposits are located at or near the surface of the Earth, surface-mining methods are used to remove the minerals.

Types of surface mines include open pits, surface coal mines, and quarries.

Open-pit Mining Open-pit mining is used to remove

large, near-surface deposits of economically important minerals such as gold and copper.

Ore is mined downward, layer by layer, in an open-pit mine.

Explosives are often used to break up the ore.

QuarriesQuarries are open pits that are

used to mine building stone, crushed rock, sand, and gravel.

Coal that is near the surface is removed by surface coal mining.

Surface coal mining is sometimes known as strip mining because the coal is removed in strips that may be as wide as 50 m and as long as 1 km.

This quarry in northwest Georgia is an open pit used to mine granite.

Subsurface Mining Subsurface mining methods are used when

mineral deposits are located too deep within the Earth to be surface mined.

Subsurface mining often requires that passageways be dug into the Earth to reach the ore.

If a mineral deposit extends deep within the Earth, however, a vertical shaft is sunk.

Responsible Mining

Mining gives us the minerals we need, but it may also create problems.

Mining can destroy or disturb the habitats of plants and animals.

Also, the waste products from a mine may get into water sources, which pollutes surface water and groundwater.

Mine ReclamationOne way to reduce the potential harmful effects of mining is to return the land to its original state after the mining is completed.

The process by which land used for mining is returned to its original state or better is called reclamation.

Reclamation of mined public and private land has been required by law since the mid-1970s.

The Use of MineralsMineral Uses Copper - electrical wire, plumbing, coins Diamond - jewelry, cutting tools, drill bits Galena - batteries, ammunition Gibbsite - cans, foil, appliances, utensils Gold -jewelry, computers, spacecraft, dentistry Gypsum - wallboards, plaster, cement Halite - nutrition, highway de-icer, water softener Quartz - glass, computer chips Silver - photography, electronics products, jewelry Sphalerite - jet aircraft, spacecraft, paints

Metallic Minerals Some minerals are metallic. Metallic minerals have shiny surfaces,

do not let light pass through them, and are good conductors of heat and electricity.

Metallic minerals can be processed into metals that are strong and do not rust. These properties make metals desirable for use in aircraft, automobiles, computers, communications and electronic equipment, and spacecraft.

Nonmetallic Minerals Other minerals are nonmetals. Nonmetallic minerals have shiny or dull

surfaces, may let light pass through them, and are good insulators of electricity.

Nonmetallic minerals are some of the most widely used minerals in industry.

For example, calcite is a major component of concrete, which is used in building roads, buildings, bridges, and other structures.

Industrial sand and gravel, or silica, have uses that range from glassmaking to producing computer chips.

Gemstones Some nonmetallic minerals, called gemstones,

are highly valued for their beauty and rarity rather than for their usefulness.

Important gemstones include diamond, ruby, sapphire, emerald, aquamarine, topaz, and tourmaline.

Color is the most important characteristic of a gemstone. The mass of a gemstone is expressed in a unit

known as a carat. One carat is equal to 200 mg.