CHAPTER 1Minerals of the Earth’s Crust

Section 1: What is a Mineral?

A mineral is a naturally formed, inorganic solid that has a definite crystalline structure.

Mineral Structure

Elements are pure substances that cannot be broken down into simpler substances by ordinary chemical means.

 

All minerals contain one or more of the 92 naturally occurring elements

4 Questions to determine if an object is a mineral:

1. Is it a solid?

 

Minerals can’t be gases or liquids

 

2. Is it nonliving material?

A mineral is inorganic, meaning it isn’t made of living things

3. Does it have a crystalline structure?

Minerals are crystals, which have a repeating inner structure that is often reflected in the shape of a crystal

 

Minerals generally have the same chemical composition throughout

 

4. Is it formed in nature?

 

Crystalline materials made by people aren’t classified as minerals

Atoms and Compounds

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

Minerals are made up of atoms of one or more element

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

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

 

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

Two Groups of Minerals

The most common classification of minerals is based on chemical composition. They are divided into two groups based on their chemical composition: Silicate minerals or Nonsilicate Minerals

Silicate Minerals: Silicon and oxygen are the 2 most common

elements in the Earth’s crust

Minerals that contain a combination of silicon and oxygen are called silicate minerals

They make up more than 90% of the Earth’s crust and the rest is made up of nonsilicate minerals

Nonsilicate Minerals:

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

6 Major Classes of Nonsilicate Minerals:

1. Native elements – made of only one element

Examples: copper, gold, and silver

 

Used in communications and electronics equipment

COPPER GOLD SILVER

2. Carbonates – contain combinations of carbon and oxygen

 

Example: Calcite

Used in cement, building stones, and fireworks

3. Halides – form when fluorine, chlorine, iodine, or bromine combine with sodium, potassium or calcium

 

Example: Fluorite

 

Are used in the chemical industry and in detergents

4. Oxides – formed with an element combines chemically with oxygen

 

Example: Corundum

 

Used to make abrasives, aircraft parts, and paint

5. Sulfates – contain sulfur and oxygen

 

Example: Gypsum

Used in cosmetics, toothpaste, cement, and paint

6. Sulfides – contain one or more elements, such as lead, iron, or nickel, combined with sulfur

 

Example: Galena

Used to make batteries, medicines, and electronic parts

Section 2: Identifying

Minerals

Bellringer: How do you describe what you see, feel,

and smell?

List as many phrases as you can to describe each mineral given.

Organize your phrases into different categories, such as color, shape, and luster.

Do any minerals have a specific smell?

Color The same mineral can come in a variety of colors

 

Impurities, exposure to air, etc can change colors of minerals and therefore isn’t the best way to identify minerals

Luster The way a surface reflects light is called

luster

When you say something is shiny or dull, you are describing luster

If a mineral is shiny, it has a metallic luster

If the mineral is dull, its luster is either submetallic or nonmetallic

Streak The color of a mineral in powdered form is

called the mineral’s streak.

Streak can be found by rubbing the mineral against a piece of unglazed porcelain called a streak plate

The mark left on the plate is called the streak

Streak is not affected by air or water so it is more reliable than using color in identifying a mineral

Cleavage and Fracture

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

Cleavage

Fracture

Hardness

A mineral’s resistance to being scratched is called hardness

Use Mohs hardness scale to determine hardness

The greater a mineral’s resistance to being scratched it, the higher the mineral’s rating is

Use a reference material to try and scratch your mineral. If the reference mineral scratches your mineral, the reference mineral is harder than your mineral

Density

Density if the measure of how much matter is in a given amount of space

It is a ratio of an object’s mass to its volume

Measured in grams per cubic centimeter.

Measured in grams per cubic centimeter (g/cm3)

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

Special Properties

Fluorescence

Calcite and fluorite glow under ultraviolet light

Magnetism

Both magnetite and pyrrhotite attract iron

Chemical Reaction

Calcite will become bubbly, or “fizz” when a drop of weak acid is placed on it

Calcite in Vinegar

Taste

Halite has a salty taste

Optical Properties

A thin, clear piece of calcite placed over an image will cause a double image.

Radioactivity

Minerals that contain radium or uranium can be detected by a Geiger counter

Section 3The Formation, Mining, and use of Minerals

Minerals form in a variety of environments in the Earth’s crust

The environment in which a mineral forms will determine it’s properties

Environments may be on or near the Earth’s surface or deep beneath the Earth’s surface

Mining

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

Rocks and minerals are removed by one of two methods – surface mining or subsurface mining

Surface Mining: Types of surface mines include open pits,

surface coal mines, and quarries

Open pit mining is used to remove large, near surface deposits of economically important minerals such as gold and copper.

Surface coal mines are sometimes used as strip mines because the coal is removed in strips that may be as wide as 50 meters and as long as 1 kilometer.

Quarries are open pits that are sued to mine building stone, crushed rock sand and gravel.

Subsurface Mining

This method is used when mineral deposits are located too deep within the Earth to be surfaced mined

Often requires passageways be dug into the Earth to reach the ore

If a mineral deposit extends deep within the Earth, a vertical shaft is sunk which my connect a number of passageways that intersect the ore at different levels

Responsible Mining

Mining gives us the minerals we need, but it also creates a lot of problems like destruction of habitats and pollution of water sources.

Mine Reclamation One 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 has been required by law since the mid 1970s

We can also help by reducing our need for minerals by recycling many mineral products we use, like aluminum

A Reclaimed mine site, one of my favorite reclaimed mine sites. This is a former Limestome Quarry, located in central Florida. It was reclaimed as a Golf Course, with a slope of 131 and is so difficult to play it is truly great, if your shots are VERY accurate. As you can see, even the fairways slope in every direction, and the Rough, well they rate a 10.

Reclamation of a mine site in progress, note the silt fences (rows of material that look like a fence). These are to prevent any solid particulates from the disturbed soil from entering the water through runoff from rainfall. Modern mining companies take every precuation to ensure the preservation of the natural resources of the community in which they reside and operate

The Use of Minerals

Metallic Minerals

Have shiny surfaces, do not let light pass through them and are good conductors of heat and electricity

Can be processed into metals that are strong and do not rust

Can be pounded and pressed into various shapes or stretched thinly without breaking

Properties make them desirable for use in aircraft, automobiles, computers, communications and electronic equipment and spacecraft

Nonmetallic Minerals

Have shiny or dull surfaces, may let light pass through them and are good insulators of electricity.

Some of the most widely used minerals in industry

Gemstones Nonmetallic minerals are highly valued for their

beauty and rarity rather than their usefulness.

Include diamond, ruby, sapphire, emerald, aquamarine, topaz and tourmaline

Color is the most important characteristic

Must also be durable to withstand polishing

The mass is represented with a carat.