What is a Mineral?What is a Mineral?

• A mineral is a:A mineral is a:– Naturally occurring,Naturally occurring,– Inorganic,Inorganic,– Crystalline solid,Crystalline solid,– That has a definite chemical That has a definite chemical

composition.composition.

Some MineralsSome Minerals

What is a Rock?What is a Rock?

• A rock is a:A rock is a:– Naturally formed,Naturally formed,– Consolidated material,Consolidated material,– Composed of grains of one or Composed of grains of one or

more minerals.more minerals.

Some RocksSome Rocks

Mineral Mineral CharacteristicsCharacteristics

•Minerals are classified based on their physical physical propertiesproperties and chemical chemical properties.properties.

How Do We Identify How Do We Identify Minerals?Minerals?

• We identify minerals using We identify minerals using physical properties of:physical properties of:– Color and streakColor and streak– LusterLuster– HardnessHardness– CleavageCleavage– FractureFracture

Color and StreakColor and Streak

• Color is the first thing that most people notice about minerals.– Color is a useful property but many

minerals are found in a variety of colors.

• Streak is the pulverized color of a mineral.– Streak is determined by scraping the

sample across a porcelain plate.

LusterLuster

• LusterLuster is the quality and intensity is the quality and intensity of the light that is reflected from of the light that is reflected from the surface of a mineral.the surface of a mineral.

• LusterLuster is described as metallic or is described as metallic or non-metallic.non-metallic.– Non-metallicNon-metallic is more common, most is more common, most

importantly is glassy.importantly is glassy.– Earthy lusterEarthy luster is uncommon but is uncommon but

appears silky, or pearly.appears silky, or pearly.

EarthyEarthy and Metallic and Metallic LusterLuster

HardnessHardness

• HardnessHardness is a minerals is a minerals resistance to being scratched, resistance to being scratched, or the “scratchability” of a or the “scratchability” of a mineral. mineral. – In order for a mineral to scratch In order for a mineral to scratch

another it must be harder.another it must be harder.– Frederich MohsFrederich Mohs made up a scale, made up a scale,

called the Mohs Scale, to compare called the Mohs Scale, to compare hardness.hardness.

CleavageCleavage

• CleavageCleavage is the tendency of a is the tendency of a mineral to break along one or mineral to break along one or more smooth, flat, lustrous more smooth, flat, lustrous surfaces.surfaces.– Cleavage is described as perfect, Cleavage is described as perfect,

good, or poor.good, or poor.– Different minerals have different Different minerals have different

planes of cleavage.planes of cleavage.• Examples: mica has one perfect plane, Examples: mica has one perfect plane,

halite has three perfect planeshalite has three perfect planes

FractureFracture

• FractureFracture is the way a mineral is the way a mineral breaks other than cleaving.breaks other than cleaving.– FractureFracture is an irregular break is an irregular break

patternpattern– FractureFracture can be described as can be described as

unevenuneven, , conchoidalconchoidal (shell-like), (shell-like), splinterysplintery, , earthyearthy (like clay) (like clay)

Formation of Formation of MineralsMinerals

All minerals are crystallinecrystalline, ,made of atoms arranged in a pattern.

CrystalsCrystals are minerals with geometric shapes and smooth flat surfaces called faces.

Each kind of mineral has its own crystal shape and will develop into this form if it has room to grow w/o restrictions.

Various CrystalsVarious Crystals

6 Basic Crystal Systems6 Basic Crystal Systems

• CubicCubic• HexagonalHexagonal• OrthorhombicOrthorhombic• MonoclinicMonoclinic• TetragonalTetragonal• TriclinicTriclinic

Chemical CompositionChemical Composition

• All minerals are made of elements and some minerals can be identified by their special chemical composition.

• Some minerals are made up of only one element (such as gold, copper, sulfur).

• Most minerals are made of compounds, two or more elements chemically combined.

Chemical Composition - Chemical Composition - SilicatesSilicates

• SilicatesSilicates are the most common minerals and are combinations of silicon and oxygen with other elements.

• Examples are quartz, feldspar, Examples are quartz, feldspar, mica and hornblende.mica and hornblende.

SilicatesSilicates

Chemical Composition - Chemical Composition - CarbonatesCarbonates

• CarbonatesCarbonates are minerals which are compounds of 1 carbon 1 carbon atom and 3 oxygen atomsatom and 3 oxygen atoms.

• Examples are calcite and dolomite.

CarbonatesCarbonates Calcite

Dolomite

Calcite Color Varieties

Chemical Composition – Chemical Composition – OxidesOxides and and SulfidesSulfides

• In an oxideoxide, the mineral iron iron combines with combines with oxygenoxygen.– Example is magnetitemagnetite

• In a sulfidesulfide, the mineral iron iron combines with combines with sulfursulfur.– Example is pyritepyrite (fool’s gold)

Oxides and SulfidesOxides and Sulfides

Magnetite (Lodestone) and Pyrite (Fool’s Gold)

Structure of MineralsStructure of Minerals

• StructureStructure refers to the arrangement of the atoms in a mineral.

• SiliconSilicon and oxygenoxygen, the most common elements in the Earth’s crust, combine chemically to form a structural unit in the shape of a tetrahedrontetrahedron (a four-sided solid triangle)