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Minerals

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What is a Mineral?

Naturally Occurring

Inorganic

Solid Definite Chemical Formula

Definite Crystal Structure

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Naturally Occurring

Formed by natural processes not in thelaboratory.

Is an ice cube a mineral?

Is the ice on the windshield of a car a mineral?

Minerals manufactured by humans are not

considered minerals.

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Inorganic

Formed by inorganic processes; not living

Minerals are not made from living things.

Coal is made of carbon. Is it a mineral?

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Solid

Minerals cannot be a gas or a liquid.

- H2O as ice in a glacier is a mineral, but

water is not.

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Definite Crystal Structure

Highly ordered atomic arrangement ofatoms in regular geometric patterns

Apatite Feldspar Diamond Quartz

Minerals are crystals with a repeated inner

structure.

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Definite Chemical Formula

Minerals areexpressed by aspecific chemical

formula.

- Gold (Au)- Calcite (CaCO3)- Quartz (SiO2)- Pyrite (FeS

2)

Minerals made of onlyone type of atom

(element) are callednative elements.

Gold

Copper

Silver

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Types of minerals

Minerals are most commonly classified bychemical composition.

The 2 main groups are silicates andnonsilicates.

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Silicates Minerals containing a combination of silicon (Si)

and oxygen (O) (most common elements in theearths crust)

Silicate minerals comprise about 90% of theEarths crust.

Silicates minerals often contain other elementssuch as aluminum, iron, magnesium, and

potassium. Granite is a rock comprised of the minerals

feldspar, biotite mica and quartz.

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Feldspar

Feldspar minerals make uphalf of the Earths crust and isthe main component of most

of the rocks found on theEarths surface.

Feldspar

Feldspar contains Si, O, Al, K,Na, and Ca

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Biotite Mica

soft and shinyminerals that

separate easily intosheets

biotite is one varietyof mica

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Quartz

silicon dioxide ( SiO2)

is the basic building

block of many rocks

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Nonsilicates

minerals that do not contain thecombination of Si and O

some of these minerals are made up of C,O, F, and S

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Classes of nonsilicates

Native Elements

Carbonates

Halides Oxides

Sulfates

Sulfides

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Native Elements

Native elements are

composed of only 1element

About 20 existincluding Au, Pt, C,

Cu, S and Ag

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Carbonates contain the

combinations ofcarbon and Oxygen intheir chemical

structure calcite (CaCO3 ) is an

example

carbonates are used

in cement, buildingstones and fireworks

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Halides form when atoms

containing fluorine,chlorine, iodine, orbromine (halogens)combine with potassium

or calcium Halite (NaCl) is better

known as rock salt

Fluorite can have many

different colors Halides are often used in

making fertilizers

Fluorite

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Oxides

compounds formedwhen elements likealuminum or ironbond with oxygen

Corundum (Al2O3) andMagnetite (Fe3O4) areimportant oxides

Are used in abrasivesand airplane parts

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Sulfates

minerals containing sulfurand oxygen (SO4)

gypsum (CaSO4

* 2H2

O)is a common example

makes the white sand atWhite Sands NationalMonument in NM

sulfates are commonlyused in cosmetics,toothpaste and paints

Gypsum

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Sulfides

minerals containing oneor more elements such aslead, iron, or nickel

combines with sulfur

Galena (PbS) is a sulfide

Sulfides are used to makebatteries, medicines and

electronic parts

Galena

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Composition of the Earths Crust

- Oxygen (O)

- Silicon (Si)- Aluminum (Al)- Iron (Fe)

- Calcium (Ca)- Sodium (Na)- Potassium (K)

- Magnesium (Mg)

Eight Elements that make up over 98%of Earths Crust

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Where Do Minerals Come From?

Magma

Evaporation

In general, minerals form in two ways:Cooling magma - Crystallization of melted materials

From solution - Crystallization of materials dissolved in water

At the surface

Beneath thesurface

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Magma

Magma is molten material from the mantlethat hardens to form rock.

Lava is magma that reaches the surface.

Minerals form as hot magma cools insidethe crust, or as lava hardens on thesurface.

When these liquids cool to the solid state,they form crystals.

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Size of Crystals

Magma closer to the surface cools muchfaster, producing smaller crystals.

Slow cooling leads to the formation oflarge crystals.

When magma remains deep below thesurface, it cools slowly over manythousands of years.

The chemical composition of the magma

The amount of gas the magma contains

The rate at which the magma cools

Depends of several factors:

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Minerals from Hot Water Solutions

This can happen on

the ocean floor whenocean water seepsdown through cracksin the crust.

When a hot water solution begins to cool, theelements and compounds leave the solution andcrystallize as minerals.

A solution is a mixture in which one substancedissolves in another.

Sometimes, the elements that form a mineral

dissolve in hot water and form a solution.

http://oceanexplorer.noaa.gov/explorations/02fire/logs/magicmountain/merlin/merlin_fly.html

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Minerals formed by Evaporation

Gypsum

Calcite crystals

Minerals containing potassium

Several other useful minerals also from by

the evaporation of seawater:

Minerals can also form when solutions

evaporate. Example: salt from sea water

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Minerals formed by Metamorphism

When rocks are put under extreme heatand pressure, the chemical composition ofthe rock can change, forming newminerals.

Examples: calcite, garnet, graphite,

hematite, magnetite, mica and talc.

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How Are Minerals Identified?

Color

Luster

Hardness

Streak

Density

Crystal Shape

Cleavage and Fracture

Special Properties

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Color

Usually the first and most easily observed

QUARTZROSE QUARTZ SMOKY QUARTZ

- Some minerals are the same color as others

- Some minerals can have many colors

Not a reliable way to identify a mineral

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Luster

General appearance of a mineral surface inreflected light

Glassy-Obsidian

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Examples of luster Metallic

Greasy: resembles the way petroleum jelly or a greasysurface reflects light

Silky: resembles the way silk reflects light

Earthy: dull, may be rough or dusty

Waxy

Adamantine: resembles the way a diamond shines

Vitreous: similar to glass

Resinous: resembles the way plastic reflects light

Pearly: resembles the way pearls shine

Pitchy looks like tar

Fibrous looks like fibers

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Hardness

Resistance to scratching by different items;scratchability

Mohs Hardness Scale is used to determine thehardness of minerals by comparing them tosubstances of known hardness:

< 2 fingernail

3 penny

~ 5 Steel of a pocket knife5.5 Window Glass

6.6 Steel of a file

7 Quartz crystal

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Mohs Mineral Hardness Scale

1) Talc

2) Gypsum

3) Calcite

4) Flourite

5) Apatite

6) Feldspar

7) Quartz

8) Topaz

9) Corundum

10) Diamond

Softest

Hardest

1

2

3

4

5

6

7

8

9

10

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Streak

The color of a finely powdered mineral

Determined by rubbing the mineral on a piece

of unglazed porcelain (streak plate)

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Density The amount of matter in a given space

Specific Gravity is the comparison of a substancesdensity to the density of water

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Crystal Shape

Minerals have acharacteristic crystal

shape resulting fromthe atomic packing ofthe atoms when themineral is forming

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Cleavage and Fracture

Cleavage is the tendency of a mineralto split or crack along parallel or flatplanes

Fracture occurs when a mineral breaksat random lines instead of at consistentcleavage planes.

BIOTITE QUARTZ Obsidian

No Cleavage1 Direction of Cleavage Conchoidal Fracture

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Fracture

S i l P ti

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Special Properties Magnetism (Magnetite)

Taste (Halite)

Smell (Sulfur)

Reaction to HCl (Calcite)

Double refractive - a thin, clear piece ofcalcite placed over an image will cause adouble image

Radioactivity - minerals containing radium or uranium

can be detected by a Geiger counter

Glowing under ultraviolet light (Fluorite)

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Economic Importance of Minerals

Minerals are in many things we see anduse everyday such as; bricks, glass,

cement, plaster, iron, gold

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Every American Requires 40,000Pounds of New Minerals per Year

at this level of consumption the average newborn infantwill need a lifetime supply of:-795 lbs of lead (car batteries, electric components)

-757 lbs of zinc (to make brass, rubber, paints)-1500lbs of copper (electrical motors, wirings-3593 lbs aluminum (soda cans, aircraft)-32,700 lbs of iron (kitchen utensils, automobiles,buildings)

-28,213 lbs of salt (cooking, detergents)-1,238,101 lbs of stone, sand, gravel, cement (roads,homes, etc.)