So what is a mineral?So what is a mineral?

What are the What are the characteristics of all characteristics of all

minerals?minerals?

1. A mineral occurs naturally.1. A mineral occurs naturally.

2. A mineral is solid.2. A mineral is solid.

3. A mineral has a definite 3. A mineral has a definite chemical composition.chemical composition.

4. A mineral’s atoms are 4. A mineral’s atoms are arranged in an orderly pattern.arranged in an orderly pattern.

5. A mineral is inorganic (was 5. A mineral is inorganic (was never alive)never alive)

Of the almost 4000 known minerals, Of the almost 4000 known minerals, only about 30 are common.only about 30 are common.

The most common are The most common are quartz,feldspar,mica, and calcite.quartz,feldspar,mica, and calcite.

These minerals make up most These minerals make up most of the rocks found in the of the rocks found in the

Earth’s crust.Earth’s crust.

In fact, over In fact, over 60%60% of the Earth’s of the Earth’s crust is made up of the family crust is made up of the family of minerals known as feldspar!of minerals known as feldspar!

To be able to identify these and To be able to identify these and other minerals, we need to look other minerals, we need to look

at the at the properties properties used to used to separate and distinguish these separate and distinguish these

minerals.minerals.

Remember!:Remember!:

Rarely is a mineral identified Rarely is a mineral identified by a single property.by a single property.

These properties need to be These properties need to be considered together to considered together to

correctly identify a mineral.correctly identify a mineral.

Color is the most easily Color is the most easily observed mineral property observed mineral property

and the and the leastleast useful! useful!

Some exceptions to the color Some exceptions to the color rule would be rule would be cinnabarcinnabar, , which is always red, and which is always red, and

malachitemalachite, which is green., which is green.

Many minerals have a similar Many minerals have a similar color.color.

Many minerals can turn Many minerals can turn colors due to impurities, or colors due to impurities, or they can change colors in they can change colors in

various circumstances.various circumstances.

For example, pure quartz is For example, pure quartz is colorless or white, colorless or white,

impurities can make the impurities can make the mineral rose, purple or pink!mineral rose, purple or pink!

Discuss the following!Discuss the following!

How many of the characteristics How many of the characteristics of minerals can you name?of minerals can you name?

Why isn’t color a very good Why isn’t color a very good property to identify most property to identify most

minerals?minerals?

Luster refers to the way a mineral Luster refers to the way a mineral shines in reflected light.shines in reflected light.

Notice the difference between Notice the difference between these two minerals?these two minerals?

The mineral on the left has a The mineral on the left has a metallic lustermetallic luster, the one on , the one on

the right, a the right, a nonmetallic nonmetallic lusterluster..

There are several terms used to There are several terms used to describe nonmetallic luster. describe nonmetallic luster.

Examples could be Examples could be vitreousvitreous, like , like the quartz on the left, or the quartz on the left, or pearlypearly, ,

like the gypsum on the right.like the gypsum on the right.

Other terms that might be used Other terms that might be used include include greasy, dull, greasy, dull, and and earthyearthy..

Can you tell which of these has an Can you tell which of these has an earthy luster and which has a earthy luster and which has a

vitreous luster?vitreous luster?

Earthy

Vitreous

StreakStreak of a mineral is the color of a mineral is the color of its powder when rubbed on of its powder when rubbed on

an unglazed white tile.an unglazed white tile.

The streak is often not the same The streak is often not the same color as the mineral. color as the mineral.

A minerals color may vary, but A minerals color may vary, but the streak rarely will!the streak rarely will!

The The cleavage cleavage of a mineral is its of a mineral is its tendency to split easily or to tendency to split easily or to separate along flat surfaces.separate along flat surfaces.

Cleavage can even be observed Cleavage can even be observed on tiny mineral grains making on tiny mineral grains making

it a very useful property!it a very useful property!

MicaMica is probably the best is probably the best example as it splits into thin example as it splits into thin sheets. It is said to have one sheets. It is said to have one

perfect cleavage.perfect cleavage.

FeldsparFeldspar splits readily in two splits readily in two directions, always at or near directions, always at or near

right angles.right angles.

CalciteCalcite and and galenagalena cleave in three cleave in three directions.directions.

They are said to have three good They are said to have three good cleavages.cleavages.

Not all minerals show cleavage.Not all minerals show cleavage.

Those that don’t break along cleavage Those that don’t break along cleavage surfaces are said to have surfaces are said to have fracturefracture..

Discuss the following!Discuss the following!

There are four common minerals, There are four common minerals, how many can you name?how many can you name?

Of the four common minerals, Of the four common minerals, which one makes up over 60% which one makes up over 60%

of the Earth’s crust?of the Earth’s crust?

The The hardnesshardness of a mineral is its of a mineral is its resistance to being scratched.resistance to being scratched.

Diamond is the hardest of all Diamond is the hardest of all minerals, and talc is the softest.minerals, and talc is the softest.

Friedrich Friedrich MohsMohs devised a hardness devised a hardness scale. scale.

In this scale, ten wellknown minerals In this scale, ten wellknown minerals are given numbers from one to ten.are given numbers from one to ten.Lets take a look at the ten minerals Lets take a look at the ten minerals used and some of the simple tests.used and some of the simple tests.

Talc Talc (left) is the softest and has a (left) is the softest and has a hardness of 1. A soft pencil lead hardness of 1. A soft pencil lead

will scratch talc.will scratch talc.GypsumGypsum is a bit harder and has a is a bit harder and has a

hardness of 2. A fingernail hardness of 2. A fingernail scratches gypsum.scratches gypsum.

CalciteCalcite (left) has a hardness of 3 and a (left) has a hardness of 3 and a copper penny just scratches it.copper penny just scratches it.

FluoriteFluorite has a hardness of 4 and it can has a hardness of 4 and it can be scratched by an iron or brass nail.be scratched by an iron or brass nail.

ApatiteApatite (left) has a hardness of 5 (left) has a hardness of 5 and can be scratched by a steel and can be scratched by a steel

knife blade.knife blade.FeldsparFeldspar has a hardness of 6 and it has a hardness of 6 and it

will scratch a window glass.will scratch a window glass.

QuartzQuartz (left), with a hardness of 7, (left), with a hardness of 7, is the hardest of the common is the hardest of the common

minerals. It easily scratches hard minerals. It easily scratches hard glass and steel.glass and steel.

TopazTopaz has a hardness of 8 and will has a hardness of 8 and will scratch quartz.scratch quartz.

CorundumCorundum (left) has a hardness of 9. (left) has a hardness of 9. Corundum will scratch topaz.Corundum will scratch topaz.

DiamondDiamond with its hardness of 10 can with its hardness of 10 can easily scratch the rest of the easily scratch the rest of the

minerals. minerals.

Discuss the following!Discuss the following!

Does this mineral show Does this mineral show cleavage or fracture?cleavage or fracture?

Of the four most common Of the four most common minerals, which is the highest minerals, which is the highest

hardness?hardness?

Crystal shapeCrystal shape can be a useful can be a useful property to identify minerals if property to identify minerals if the minerals have had the time the minerals have had the time

and space to form crystals. and space to form crystals. Most mineral grains that are Most mineral grains that are

found in rocks, lack the room to found in rocks, lack the room to grow.grow.

Specific gravitySpecific gravity tells you how tells you how many times as dense as water many times as dense as water

the mineral is.the mineral is.

Pure gold can have a specific Pure gold can have a specific gravity as high as 19.3!gravity as high as 19.3!

CalciteCalcite is calcium carbonate, is calcium carbonate, CaCOCaCO33. If a drop of weak . If a drop of weak

hydrochloric acid is placed on hydrochloric acid is placed on calcite, the acid bubbles as calcite, the acid bubbles as carbon dioxide is released.carbon dioxide is released.

Malleable

Magnetic

Radioactive

Flourescence

Taste

Minerals that can be hammered Minerals that can be hammered thin or shaped are said to show thin or shaped are said to show

these properties.these properties.

Can you think of a mineral that Can you think of a mineral that might be shaped or hammered?might be shaped or hammered?

GoldGold would be a perfect would be a perfect example!example!

Some minerals Some minerals that contain that contain

Iron, are Iron, are magnetic and magnetic and can be picked can be picked

up by a up by a magnet.magnet.

This is the state of This is the state of glowing while glowing while

under a ultraviolet under a ultraviolet light.light.

Some minerals Some minerals even glow once even glow once

the light is turned the light is turned off!off!

Some minerals, Some minerals, such as this such as this

uraniniteuraninite, are , are radioactive.radioactive.

They give off They give off subatomic subatomic

particles that will particles that will activate a activate a Geiger Geiger

countercounter..

HaliteHalite (rock salt) (rock salt) can be identified can be identified

by its taste.by its taste.

This practice is This practice is not not

recommended!recommended!