RocksRocks and and MineralsMinerals

Chapters 10-11Chapters 10-11

RocksRocksEarth’s crust is made of Earth’s crust is made of rock.rock.Rocks are Rocks are mixtures mixtures of of mineralsminerals and sometimes and sometimes other materialsother materials..

When studying a When studying a rock rock samplesample, geologists observe , geologists observe the rock’s:the rock’s:ColorColorTextureTextureChemical compositionChemical composition

Most rocks are made up of Most rocks are made up of grainsgrains, , particles of particles of mineralsminerals, or other , or other rocks.rocks.

TextureTexture is the look that results is the look that results from:from:

SizeSizeShapeShapePatternPattern of rock’s of rock’s grainsgrains

CoarseCoarse-grained---grained--large/easy to see.large/easy to see.FineFine-grained – -grained – small, even small, even microscopic.microscopic.

Grains in rock often form a Grains in rock often form a patternpattern..

FlatFlat layers layers ((stratastrata))

Wavy, Wavy, swirlingswirling patternspatterns

Rows of Rows of beadsbeads

RandomRandom or no pattern or no pattern

Some rocks have Some rocks have NO grainNO grain, , because they cooled too because they cooled too quickly when they quickly when they formedformed..

There are There are 33 groups of groups of rocks:rocks:

IgneousIgneousMetamorphicMetamorphicSedimentarySedimentary

Igneous RocksIgneous Rocks

Formed from the cooling of Formed from the cooling of moltenmolten (melted) (melted) rockrock..

Examples:Examples:

pumice, granite, basaltpumice, granite, basalt

Sedimentary RocksSedimentary RocksFormed when particles of other rocks, plants, or animals are cemented together.Examples:

Sandstone, breccia, siltstone

Formed when existing rock is changed by heat, pressure, or chemical reactions.Examples:

gneiss, schist, phyllite

Metamorphic RocksMetamorphic Rocks

The Rock CycleThe Rock Cycle

MineralsMineralsA mineral:A mineral:occurs occurs naturallynaturallyIs Is inorganicinorganicIs Is solidsolidHas a Has a crystal structurecrystal structureHas a definite Has a definite chemical chemical compositioncomposition

MineralsMineralsThere are There are 30003000 minerals. minerals.100100 are common. are common.2020 minerals make up minerals make up mostmost of of

the the rock’srock’s of Earth’s crust of Earth’s crust ((rockrock--formingforming minerals). minerals).

Mineral FormationMineral FormationMinerals form through:Minerals form through:

Crystallization of Crystallization of meltedmelted materials.materials.

Crystallization of Crystallization of materialsmaterials dissolved in dissolved in waterwater..

CrystalsCrystalsRepeating Repeating

patternspatterns of of a mineral’s a mineral’s particlesparticles that form a that form a solidsolid..

MineralsMineralsAll minerals contain All minerals contain certaincertain

elements in elements in definitedefinite amounts. amounts.Most minerals are Most minerals are compoundscompounds

((twotwo or more or more elementselements).).SilverSilver and and goldgold are considered are considered

minerals.minerals.

Mohs Hardness Mohs Hardness ScaleScale

The Mohs The Mohs hardness scale hardness scale ranks ten ranks ten mineralsminerals from from softestsoftest to to hardesthardest..

Talc 11Gypsum 2Calcite 33Fluorite 4Apatite 55Feldspar 6Quartz 7Topaz 8Sapphire 99DiamondDiamond 10

Minerals are ranked Minerals are ranked according to:according to:

ColorColor

StreakStreak– the – the colorcolor of of a mineral’s a mineral’s powderpowder..

Luster – Luster – how shiny a how shiny a mineral is.mineral is.

Density—Density—massmass per unit per unit volumevolume

(specific gravity)(specific gravity)

CleavageCleavage – – breaking of a breaking of a mineralmineral along along a regular a regular lineline..

FractureFracture – irregular – irregular breakingbreaking of a mineral. of a mineral.

FluorescenceFluorescenceMinerals that Minerals that glowglow under under ultravioletultraviolet light. light.

MagnetismMagnetismMagnetism occurs Magnetism occurs naturallynaturally in some in some mineralsminerals, such as , such as magnetitemagnetite..