Earths Rocks & MineralsEarths Rocks & Minerals

Chapter 15Chapter 15

MineralsMinerals

Minerals are very important in everyday Minerals are very important in everyday life. Minerals, bricks, and glass are some life. Minerals, bricks, and glass are some examples of how we use minerals.examples of how we use minerals.

MineralMineral- is a naturally occurring, inorganic - is a naturally occurring, inorganic solid with a definite chemical composition solid with a definite chemical composition and an orderly arrangement of atoms.and an orderly arrangement of atoms.

There are about 4,000 minerals on Earth.There are about 4,000 minerals on Earth.

Mineral CharacteristicsMineral Characteristics

1)1) All minerals are formed by natural All minerals are formed by natural processes.processes. These processes occur on or These processes occur on or inside the Earth with no human inside the Earth with no human interaction. interaction.

Ex: Salt forms by the natural evaporation of Ex: Salt forms by the natural evaporation of salt water. This type of salt comes from a salt water. This type of salt comes from a mineral called Halite.mineral called Halite.

Salt water solution made in a lab is not a Salt water solution made in a lab is not a mineral.mineral.

Mineral CharacteristicsMineral Characteristics2) 2) Minerals are inorganic-Minerals are inorganic- this means that this means that

there is no Carbon is present in minerals.there is no Carbon is present in minerals.

3) 3) Every mineral is an element or compound Every mineral is an element or compound with a definite chemical composition.with a definite chemical composition.

4) 4) All minerals are crystalline solidsAll minerals are crystalline solids. And all . And all crystals have a definite volume and shape.crystals have a definite volume and shape.

CrystalsCrystals

Crystal atoms are arranged in a pattern Crystal atoms are arranged in a pattern that is repeated over and over again.that is repeated over and over again.

Ex: Graphite atoms are arranged in layers.Ex: Graphite atoms are arranged in layers.

Opal- is not a mineral because it has no Opal- is not a mineral because it has no repeated atom patterns.repeated atom patterns.

Structure of MineralsStructure of Minerals All minerals are crystalline solids.All minerals are crystalline solids. Crystalline solidsCrystalline solids-- are solids in which the are solids in which the

atoms are arranged in an orderly repeated atoms are arranged in an orderly repeated fashion.fashion.

This does not mean that all minerals look like This does not mean that all minerals look like crystals.crystals.

Ex: Ex: Rose quartz doesn’t look like a crystal Rose quartz doesn’t look like a crystal because it develops in tight spaces.because it develops in tight spaces.

Clear quartz forms in open spaces and its Clear quartz forms in open spaces and its appearance is clearly crystal shaped.appearance is clearly crystal shaped.

Crystal vs. Non-CrystalCrystal vs. Non-Crystal

Crystal FormationCrystal Formation

Crystals form in two ways:Crystals form in two ways:

1)1) From cooling MagmaFrom cooling Magma

2)2) Could form in solutionCould form in solution

Crystal Formation from MagmaCrystal Formation from Magma

The type of atoms present and the amount The type of atoms present and the amount will determine what mineral is produced.will determine what mineral is produced.

When magma cools slowly When magma cools slowly largelarge crystals crystals form.form.

When magma cools When magma cools quicklyquickly then small then small crystals form.crystals form.

Crystal Formation from SolutionCrystal Formation from Solution Crystals form minerals dissolved in water.Crystals form minerals dissolved in water.

When water evaporates, ions are left When water evaporates, ions are left behind that can combine to form crystals behind that can combine to form crystals like halite. (salt) like halite. (salt)

Or Or If there is too much substance in solution If there is too much substance in solution

the crystals could form in the solutionthe crystals could form in the solution

Quartz and Feldspar PicsQuartz and Feldspar Pics

How to Identify MineralsHow to Identify Minerals

We identify minerals by some very specific We identify minerals by some very specific physical features and properties.physical features and properties.

Color is one way to tell the difference between two Color is one way to tell the difference between two minerals but color alone is not enough.minerals but color alone is not enough.

Ex: Gold and pyrite both have the same color, but Ex: Gold and pyrite both have the same color, but they are two very different minerals. Pyrite has they are two very different minerals. Pyrite has very little value compared to gold.very little value compared to gold.

So to tell these two apart you have to look at other So to tell these two apart you have to look at other properties.properties.

Gold and PyriteGold and Pyrite

5 Major properties used to 5 Major properties used to distinguish between mineralsdistinguish between minerals

1)1) HardnessHardness

2)2) LusterLuster

3)3) Specific gravitySpecific gravity

4)4) StreakStreak

5)5) Cleavage/ fractureCleavage/ fracture

5 major properties5 major properties

1)1) Hardness- Hardness- This is This is the measure of how the measure of how easily a mineral can easily a mineral can be scratched.be scratched.

Ex: Talc, a very soft Ex: Talc, a very soft mineral can be mineral can be scratched with just scratched with just your finger nail.your finger nail.

Hardness of MineralsHardness of Minerals

Diamonds, on the Diamonds, on the other hand are the other hand are the hardest mineral.hardest mineral.

The only this that can The only this that can scratch a diamond is scratch a diamond is another diamond.another diamond.

Remember scratch Remember scratch and break are not the and break are not the same. If hit hard same. If hit hard enough a diamond enough a diamond will shatter.will shatter.

Mohs ScaleMohs Scale In 1812 the Mohs scale of mineral hardness was devised by the In 1812 the Mohs scale of mineral hardness was devised by the

German mineralogist Frederich Mohs (1773-1839), who German mineralogist Frederich Mohs (1773-1839), who selected the ten minerals because they were common or selected the ten minerals because they were common or readily available. The scale is not a linear scale, but somewhat readily available. The scale is not a linear scale, but somewhat arbitrary.arbitrary.

Hardness of some other items:Hardness of some other items: 2.5 Fingernail2.5 Fingernail 2.5–3 Gold, Silver2.5–3 Gold, Silver 3 Copper penny3 Copper penny 4-4.5 Platinum4-4.5 Platinum 4-5 Iron4-5 Iron 5.5 Knife blade5.5 Knife blade 6-7 Glass6-7 Glass 6.5 Iron pyrite6.5 Iron pyrite 7+ Hardened steel file7+ Hardened steel file

5 major properties5 major properties

2) 2) LusterLuster- This is the way a mineral reflects - This is the way a mineral reflects light.light.

This reflection could be metallic, meaning it This reflection could be metallic, meaning it shines like a metal, or non-metallic or dull shines like a metal, or non-metallic or dull or glassy looking.or glassy looking.

LusterLuster

5 major properties5 major properties

3) 3) Specific Gravity-Specific Gravity- This is the ratio of the This is the ratio of the minerals weight compared to the weight of minerals weight compared to the weight of an equal volume of water.an equal volume of water.

Ex: Specific Gravity of Gold is 19:1 or 19.Ex: Specific Gravity of Gold is 19:1 or 19.This means that gold is 19x heavier that This means that gold is 19x heavier that

water.water.How could you find out the volume of a How could you find out the volume of a

solid?solid?

5 major properties5 major properties

4) 4) StreakStreak- Is the color of a mineral when it is in - Is the color of a mineral when it is in powder form.powder form.

So if we have a solid mineral we would streak it So if we have a solid mineral we would streak it across a piece of porcelain to see what color is across a piece of porcelain to see what color is left behind.left behind.

5 major properties5 major properties5) 5) Cleavage/ Fracture-Cleavage/ Fracture- this is the way a mineral this is the way a mineral

breaks.breaks.

Minerals that break along a smooth flat surface Minerals that break along a smooth flat surface have have cleavage.cleavage.

5 major properties5 major properties Cleavage/ Fracture- Cleavage/ Fracture- Minerals that break Minerals that break

unevenly, or with rough jagged surfaces have unevenly, or with rough jagged surfaces have fracture.fracture.

Uses of MineralsUses of Minerals

GemsGems- Gems are highly - Gems are highly prized minerals due to prized minerals due to their rareness and their rareness and beauty.beauty.

They are clearer brighter They are clearer brighter and more colorful then and more colorful then common minerals.common minerals.

Gems always come from Gems always come from other minerals.other minerals.

Ex: Amethyst is a gem Ex: Amethyst is a gem that comes from Quartz. that comes from Quartz. Because it has less iron Because it has less iron in it than quartz does it in it than quartz does it has a beautiful purple has a beautiful purple color.color.

Useful GemsUseful Gems Some gems are very useful like diamonds.Some gems are very useful like diamonds.

They are not only used to make beautiful They are not only used to make beautiful jewelry but since they are the hardest jewelry but since they are the hardest mineral on Earth they are also used for mineral on Earth they are also used for cutting tools like saw blades.cutting tools like saw blades.

Rubies are used to create lasers.Rubies are used to create lasers. Quartz is used in watches and clocks.Quartz is used in watches and clocks.