Text Book Pages : 44 - 53

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

A naturally occurring, inorganic solid that has a crystal structure and a

definite chemical composition.

WWhat are the characteristics of all hat are the characteristics of all minerals?minerals?

NNow ow II SSee ee CCrystal rystal CClear!lear!

►NNaturally Occurringaturally Occurring► IInorganic (Was norganic (Was

Never Alive)Never Alive)► SSolid olid ► CCrystal Structurerystal Structure► CChemical hemical

CompositionComposition

Naturally OccurringNaturally Occurring

Must be formed by processes in the Must be formed by processes in the natural world.natural world.

Mineral Mineral QuartzQuartz forms naturally as molten material forms naturally as molten material

cools and hardens deep beneath Earth’s surfacecools and hardens deep beneath Earth’s surface..

Are man made materials likeAre man made materials like

Plastic, brick, glass, and steel can Plastic, brick, glass, and steel can be called minerals?be called minerals?

Remember:Remember:

A mineral can not form from organic materials (living A mineral can not form from organic materials (living things).things).

Is coal a mineral?Is coal a mineral?

No, it comes from the remains of plants that lived No, it comes from the remains of plants that lived millions of years ago.millions of years ago.

►Has definite volume and shapeHas definite volume and shape

►A solid in which the atoms are arranged in a pattern that repeats again and again.

►Has flat sides, called faces, that meets at sharp edges and corners.

►Like a snowflake pattern or rock candy.

► Always contains Always contains certain element in certain element in

definite proportions.definite proportions.

►Quartz has one atom Quartz has one atom of silicon for every of silicon for every

two atoms of two atoms of oxygen.oxygen.

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.

Of the almost Of the almost 40004000 known minerals, known minerals, only about only about 3030 are common. are common.

The most common are:The most common are:

quartz, feldspar, mica, and calcite.quartz, feldspar, mica, and calcite.

Fact:Fact:

Over 60% of the Earth’s crustOver 60% of the Earth’s crust isis made up of the family of made up of the family of

minerals known as minerals known as feldsparfeldspar!!

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.

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

useful! useful!

Mineral azurite is always blue.

Mineral malachite is always green.

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

Caution:Caution:

Many minerals have colors due to Many minerals have colors due to impurities, or they can change impurities, or they can change

colors in various circumstances.colors in various circumstances.

For example, pure quartz is For example, pure quartz is colorless or white, impurities colorless or white, impurities can make the mineral rose, can make the mineral rose,

purple or pink!purple or pink!

StreakStreak of a mineral is of a mineral is the color of the color of its powderits powder when rubbed on an when rubbed on an unglazed white (porcelain) tile.unglazed white (porcelain) tile.

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

A mineral’s color may vary, but A mineral’s color may vary, but the streak rarely will!the streak rarely will!

Mineral sulfur has yellow color,

but produces streak of white color on black tile.

For example, Calcite occurs in many different colors, shapes, and varieties. But every single variety of Calcite has a white streak. A streak is useful in distinguishing

two minerals with the same color but different streak.

►Minerals, which streak very light colors, can be easily identified on black streak plate.

►The way a mineral reflects light from its surface.

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..

Glassy lusterPearly luster

Silky luster

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

The The hardnesshardness of a mineral is of a mineral is it’s it’s 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 scale. devised a hardness scale.

In this scale, ten well known minerals are given numbers In this scale, ten well known minerals are given numbers from one to ten.from one to ten.

Lets take a look at the ten minerals used and some of the Lets take a look at the ten minerals used and some of the simple tests.simple tests.

Talc Talc is the softest is the softest and has a and has a hardness of 1.hardness of 1.

A soft pencil lead A soft pencil lead will scratch talc.will scratch talc.

Gypsum is a bit harder and has a hardness of 2.

A fingernail scratches gypsum.

CalciteCalcite has a has a hardness of 3.hardness of 3.

A copper penny A copper penny just scratches just scratches it.it.

Fluorite has a hardness of 4.

It can be scratched by an iron or brass nail.

ApatiteApatite has a has a hardness of 5. hardness of 5.

It can be scratched It can be scratched by a steel knife by a steel knife blade.blade.

Feldspar has a hardness of 6.

It will scratch a window glass.

Quartz,Quartz, with a with a hardness of 7, is hardness of 7, is the hardest of the the hardest of the common minerals. common minerals.

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

Topaz has a hardness of 8.

It will scratch quartz.

CorundumCorundum (left) (left) has a hardness of has a hardness of 9. 9.

Corundum will Corundum will scratch topaz.scratch topaz.

Diamond with its hardness of 10.

It can easily scratch the rest of the minerals.

►The The cleavage cleavage of a mineral is it’s of a mineral is it’s ability to split easily along flat surfaces.

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

very useful property!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 Those that don’t break along

cleavage surfaces are said to cleavage surfaces are said to have have fracturefracture..

►Minerals break in irregular way.Minerals break in irregular way.

►Crystal shapeCrystal shape can be a useful can be a useful property to identify minerals if the property to identify minerals if the minerals have had the time and minerals have had the time and space to form crystals. space to form crystals.

Most mineral grains that are found Most mineral grains that are found in rocks, lack the room to grow.in rocks, lack the room to 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, CaCO is calcium carbonate, CaCO33. .

►If a drop of weak hydrochloric acid is If a drop of weak hydrochloric acid is placed on calcite, the acid bubbles placed on calcite, the acid bubbles as carbon dioxide is released.as 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 can be

identified by its identified by its taste.taste.

This practice is This practice is not not

recommended!recommended!