MineralsMinerals

Standards/ObjectivesStandards/Objectives

Define and describe mineralsDefine and describe minerals Describe the composition and Describe the composition and structure of mineralsstructure of minerals

Describe how minerals formDescribe how minerals form Describe the physical Describe the physical properties used to identify properties used to identify mineralsminerals

What is a Mineral?What is a Mineral?

Mineral – is a naturally Mineral – is a naturally occurring, inorganic occurring, inorganic solidsolid with with a definite a definite chemicalchemical composition composition and crystalline and crystalline structurestructure..

There are about There are about 38003800 known known minerals, ~minerals, ~200200 are common. are common.

They are the building blocks of They are the building blocks of rocksrocks..

How do Minerals Form?How do Minerals Form? From the process of From the process of crystallizationcrystallization – the – the atomsatoms of a of a gas or liquid come together to gas or liquid come together to form a solid mineral.form a solid mineral.

The atoms are arranged in an The atoms are arranged in an ordered three-dimensional array ordered three-dimensional array that is that is repeatedrepeated in all in all directions.directions.

The crystal The crystal growsgrows as more atoms as more atoms are added onto the structure.are added onto the structure.

How do Minerals Form?How do Minerals Form? Minerals can form from a Minerals can form from a magmamagma as it begins to cool below its as it begins to cool below its meltingmelting point. point.

Ex: olivine and feldspar.Ex: olivine and feldspar.Photo: http://skywalker.cochise.edu/wellerr/mineral/olivine/olivineL.htm

Photo: http://www.healthstones.com/mineraldata/mineraldirectory/f/feldspar/feldspar.html

How do Minerals Form?How do Minerals Form? Minerals can form as Minerals can form as liquids liquids evaporateevaporate from from a a solutionsolution (like the (like the crystals you made in crystals you made in lab). This process is lab). This process is called called precipitationprecipitation (the minerals “fall” (the minerals “fall” out of the solution out of the solution like rain falls out of like rain falls out of the sky).the sky).

Ex: halite forms from Ex: halite forms from salt lakessalt lakes

How do Minerals Form?How do Minerals Form?

Minerals can Minerals can also form by also form by depositiondeposition – – when a solid when a solid is formed is formed from a gas.from a gas.

Ex: sulfur Ex: sulfur forms from forms from volcanic gasvolcanic gas

Photo: http://www.gccaz.edu/earthsci/imagearchive/volcanics1.htm

Photo: http://science.nationalgeographic.com/science/photos/minerals/

Chemical Composition of MineralsChemical Composition of Minerals

Minerals are made of elementsMinerals are made of elements Elements Elements cannot be broken into cannot be broken into simplersimpler substances by ordinary substances by ordinary chemical means.chemical means.

There are There are 8888 naturally occurring naturally occurring elements in Earth’s crust.elements in Earth’s crust.

There are 92 naturally occurring There are 92 naturally occurring elements all together on Earth.elements all together on Earth.

Chemical Composition of MineralsChemical Composition of Minerals

88 elements make up 98% of the crust: elements make up 98% of the crust: OxygenOxygen SiliconSilicon AluminumAluminum IronIron CalciumCalcium MagnesiumMagnesium Potassium Potassium SodiumSodium

Chemical Composition of MineralsChemical Composition of Minerals

All minerals are All minerals are crystallinecrystalline solids. solids.

A crystalline solid is a A crystalline solid is a substance whose substance whose atomsatoms are are arranged in a regular, arranged in a regular, orderly, periodically orderly, periodically repeated manner.repeated manner.

Crystal Crystal facesfaces (flat (flat planes) are the external planes) are the external expression of the expression of the mineral’s internal mineral’s internal atomicatomic structure (i.e., how the structure (i.e., how the atoms are arranged).atoms are arranged).

What makes a Mineral Unique?What makes a Mineral Unique?

There are two fundamental There are two fundamental propertiesproperties that distinguish that distinguish each mineral from all others: each mineral from all others: chemical compositionchemical composition and and crystal structurecrystal structure..

What makes a Mineral Unique?What makes a Mineral Unique?

A mineral’s chemical A mineral’s chemical compositioncomposition refers to the refers to the elementselements that form that form it.it.

Ex: Halite (NaCl), or table salt, Ex: Halite (NaCl), or table salt, is always made of a ratio of 1 is always made of a ratio of 1 sodium (Na) atom and 1 chlorine sodium (Na) atom and 1 chlorine (Cl) atom.(Cl) atom.

A mineral’s crystal A mineral’s crystal structurestructure refers to the internal framework of refers to the internal framework of the atoms that make up the mineral.the atoms that make up the mineral.

Crystal Forms and SystemsCrystal Forms and Systems

The general shape of a crystal (cubic, The general shape of a crystal (cubic, octahedral, prismatic…) is called its octahedral, prismatic…) is called its crystal crystal habithabit

If the minerals have enough space, they If the minerals have enough space, they will form in their crystalline habit. will form in their crystalline habit.

Ex: quartz crystals in the shape of Ex: quartz crystals in the shape of points.points.

If space is limited, they will have a If space is limited, they will have a massivemassive form (can’t see the crystalline form (can’t see the crystalline habit). habit).

Ex: mass of quartz where can’t see Ex: mass of quartz where can’t see individual points.individual points.

Photo: http://www.crystalminers.com/

Photo: http://www.rocksforkids.com/R&M/quartz.htm

Crystal Forms and SystemsCrystal Forms and Systems Minerals are grouped into Minerals are grouped into

crystal crystal systemssystems based on their based on their symmetrysymmetry(i.e., the angles their faces (i.e., the angles their faces make to one another). make to one another).

There are There are 66 crystal systems: crystal systems:1.1. IsometricIsometric2.2. TetragonalTetragonal3.3. HexagonalHexagonal4.4. OrthorhombicOrthorhombic5.5. TriclinicTriclinic6.6. MonoclinicMonoclinic

Physical PropertiesPhysical Properties

Are used to identify minerals.Are used to identify minerals. You will be using these You will be using these properties to identify minerals properties to identify minerals in the lab.in the lab.

Cleavage Cleavage

Cleavage – Cleavage – tendency of some tendency of some minerals to minerals to breakbreak along a along a planeplane. .

There is a There is a difference between difference between cleavagecleavage plane plane (how a mineral (how a mineral breaksbreaks) and ) and crystal crystal faceface (how (how a mineral a mineral growsgrows).).

FractureFracture Way in which minerals break Way in which minerals break

other than cleavage (e.g., other than cleavage (e.g., they do not break along a they do not break along a plane).plane).

Types of fracture:Types of fracture:

1.1. Conchoidal Conchoidal – smooth, curved – smooth, curved surfacessurfaces

FractureFracture

2.2. Splintery Splintery - - like ends of like ends of split woodsplit wood

3. Fibrous – 3. Fibrous – similar to similar to splintery, but splintery, but with a softer with a softer appearance appearance (like worn (like worn cloth)cloth)

4. Irregular 4. Irregular

Splintery

Fibrous

HardnessHardness

Resistance of the surface of a Resistance of the surface of a mineral to mineral to scratchingscratching..

It is controlled by the It is controlled by the strength of the chemical bonds.strength of the chemical bonds.

HardnessHardness

MohsMohs hardness scale – compares hardness scale – compares the relative hardness of the relative hardness of minerals. They are arranged minerals. They are arranged in order of in order of increasingincreasing hardness (1=soft and 10=hard).hardness (1=soft and 10=hard).

Mohs Hardness ScaleMohs Hardness Scale

1.1. TalcTalc

2.2. GypsumGypsum 2 ½. Fingernail2 ½. Fingernail

3.3. CalciteCalcite 3 ½. Copper 3 ½. Copper pennypenny

4.4. FluoriteFluorite

5.5. ApatiteApatite 5 ½. Glass5 ½. Glass

6.6. Orthoclase feldsparOrthoclase feldspar 6 ½. Steel6 ½. Steel

7.7. QuartzQuartz

8.8. TopazTopaz

9.9. CorundumCorundum

10.10. DiamondDiamond

Specific GravitySpecific Gravity

WeightWeight of a substance relative to of a substance relative to the weight of an equal volume of the weight of an equal volume of waterwater..

It is a measure of It is a measure of densitydensity (mass (mass divided by volume or D = m/V)divided by volume or D = m/V)

Ex: a mineral with a specific Ex: a mineral with a specific gravity of 2 weighs twice as much gravity of 2 weighs twice as much as the same volume of water.as the same volume of water.

ColorColor Most obvious property of minerals.Most obvious property of minerals. Not a reliable way to identify Not a reliable way to identify minerals. Remember the same minerals. Remember the same mineral can come in many different mineral can come in many different colors.colors.

The many colors of quartz

StreakStreak

Color of the fine Color of the fine powderpowder of a of a mineral.mineral.

More More reliablereliable for for identification than color.identification than color.

LusterLuster

How a mineral reflects How a mineral reflects lightlight.. Two main categories:Two main categories:

1. Metallic – looks like metal 1. Metallic – looks like metal surface.surface.

LusterLuster

2.2. Nonmetallic Nonmetallic – if – if nonmetallic, must be nonmetallic, must be classified as:classified as:

a. vitreous – a. vitreous – glassy glassy

b. b. pearlypearly – whitish, pearl- – whitish, pearl-like iridescencelike iridescence

c. earthy or dullc. earthy or dull

LusterLuster

d.d. resinous resinous - like - like amber or rosinamber or rosin

e. greasy – looks e. greasy – looks like it’s covered by like it’s covered by a thin layer of oil a thin layer of oil (rainbow of colors)(rainbow of colors)

TenacityTenacity Resistance of a mineral to Resistance of a mineral to breakagebreakage..1.1. Brittle – breaks and powders easily.Brittle – breaks and powders easily.2.2. MalleableMalleable – can be hammered into – can be hammered into

thin thin sheetssheets..3.3. Sectile – can be cut into thin Sectile – can be cut into thin

shavings with a knife.shavings with a knife.4.4. DuctileDuctile – can be drawn into a – can be drawn into a wirewire..5.5. Flexible – bends but does not resume Flexible – bends but does not resume

original shape (ex: copper).original shape (ex: copper).6.6. ElasticElastic – bends and regains original – bends and regains original

shape (mica).shape (mica).

Acid ReactivityAcid Reactivity

Effervesces (Effervesces (bubblesbubbles) when drop ) when drop of hydrochloric acid (HCl) is of hydrochloric acid (HCl) is placed on it.placed on it.

MagneticMagnetic

Is attracted to a magnet or Is attracted to a magnet or picks up iron filings.picks up iron filings.

Fluorescence Fluorescence

Emits visible light when Emits visible light when exposed to ultraviolet (UV) exposed to ultraviolet (UV) radiation.radiation.

Phosphorescence Phosphorescence

Continues to emit light after Continues to emit light after external light source is taken external light source is taken away.away.

Mineral ClassificationsMineral Classifications

Silicates Silicates – minerals containing – minerals containing silicon (Si) and oxygen (O). Most silicon (Si) and oxygen (O). Most abundant in Earth’s crust. Make up abundant in Earth’s crust. Make up 95% of crust.95% of crust.

CarbonatesCarbonates – contain carbon (C) and – contain carbon (C) and oxygen (O).oxygen (O).

OxidesOxides – composed of oxygen and – composed of oxygen and metals.metals.

SulfidesSulfides – contain sulfur (S) and – contain sulfur (S) and metals.metals.

SulfatesSulfates – made up of sulfate (SO – made up of sulfate (SO44--) )

and metals.and metals.

Rock Forming MineralsRock Forming Minerals Silicates – are the most Silicates – are the most

common minerals that make common minerals that make up rocks.up rocks.

1. 1. FeldsparFeldspar – most abundant – most abundant mineral, mineral, 5050% of Earth’s % of Earth’s crust.crust.a. orthoclase feldspar – a. orthoclase feldspar – contains potassium (K).contains potassium (K).b. plagioclase feldspar – b. plagioclase feldspar – contains calcium (Ca) and contains calcium (Ca) and sodium (Na).sodium (Na).

2.2. Quartz Quartz – 2 – 2ndnd most abundant most abundant

mineral, SiOmineral, SiO22..

Rock Forming MineralsRock Forming Minerals

3. 3. PyroxenePyroxene – Ex: augite – Ex: augite

4. Amphibole – Ex: hornblende4. Amphibole – Ex: hornblende

5. Mica – Ex: 5. Mica – Ex: muscovitemuscovite

6. Clay minerals – ex: kaolinite6. Clay minerals – ex: kaolinite

7. 7. OlivineOlivine