Rock Identification Rock LabRock Identification Rock Lab

Identification of all three rock groupsis based on

TEXTURE and COMPOSITION

Identification of all three rock groupsis based on

TEXTURE and COMPOSITION

the appearance of thethe appearance of therockrock

the appearance of thethe appearance of therockrock

what the rock is madewhat the rock is madeout of – type of mineralsout of – type of mineralswhat the rock is madewhat the rock is made

out of – type of mineralsout of – type of minerals

Love it, Learn it, Live it , be one with it!Love it, Learn it, Live it , be one with it!

Igneous Rock ClassificationIgneous Rock Classification

Let’s form an igneous rock• Two major types of igneous rocks

Let’s form an igneous rock• Two major types of igneous rocks

Intrusive – magma solidifies below the Earth’s surface

•magma cools very slow•crystals form interlocking “mosaic” textures•very coarse-grained visible minerals•referred to as Plutonic rocks

Intrusive – magma solidifies below the Earth’s surface

•magma cools very slow•crystals form interlocking “mosaic” textures•very coarse-grained visible minerals•referred to as Plutonic rocks

Extrusive – magma solidifies above the Earth’s surface•magma cools very fast •minerals can not be seen with un-aided eye•very fine-grained texture (no visible minerals•referred to as Volcanic rocks

Extrusive – magma solidifies above the Earth’s surface•magma cools very fast •minerals can not be seen with un-aided eye•very fine-grained texture (no visible minerals•referred to as Volcanic rocks

Igneous Rock ClassificationIdentification of igneous rocks is based on two main characteristics

Texture – the appearance of the rock due to the rate of magma cooling

Composition – the type of minerals found in the rock (mineral composition)

Igneous Rock ClassificationIdentification of igneous rocks is based on two main characteristics

Texture – the appearance of the rock due to the rate of magma cooling

Composition – the type of minerals found in the rock (mineral composition)

Textures of Igneous Rocks

Intrusive rocks (Textural terms)

phaneritic texture – crystals are visible and form a mosaic of interlocking mineral aggregates (less than 1 cm)

Textures of Igneous Rocks

Intrusive rocks (Textural terms)

phaneritic texture – crystals are visible and form a mosaic of interlocking mineral aggregates (less than 1 cm)

Interlocking crystal grainsphaneritic texture

Interlocking crystal grainsphaneritic texture

Extrusive Igneous Rocks (textural terms)Extrusive Igneous Rocks (textural terms)

aphanitic texture – crystals are too small to seeaphanitic texture – crystals are too small to see

See, you really can not see any mineral crystalsSee, you really can not see any mineral crystals

• magma cooled extremely fast (quenched)

• not enough time for atoms to combine (amorphous solid)- lacks a crystalline structure

• magma cooled extremely fast (quenched)

• not enough time for atoms to combine (amorphous solid)- lacks a crystalline structure

glassy textureglassy texture

Igneous Rock Classification LabIgneous Rock Classification LabVesicular texture- sponge like appearance, texture contains

numerous cavities or holesVesicular texture- sponge like appearance, texture contains

numerous cavities or holes

Vesicles – gas bubbles cavities Vesicles – gas bubbles cavities

Pyroclastic texture – textures created by rapidly cooling lava that is “hurled” through the air picking up fragments

(tuffaceous texture)

Pyroclastic texture – textures created by rapidly cooling lava that is “hurled” through the air picking up fragments

(tuffaceous texture)

rock fragments – pieces of rock “incorporated” into the rock (tuffaceous)

rock fragments – pieces of rock “incorporated” into the rock (tuffaceous)

Igneous Rock Classification LabIgneous Rock Classification Lab

Igneous Rock Compositionmineral composition = mineral assemblages=

chemistryThe mineral is either ferromagnesian (dark

colored) or felsic (light colored

ferromagnesian (mafic) minerals rich in Fe, Mg – creates a dark colored

rocks

Igneous Rock Compositionmineral composition = mineral assemblages=

chemistryThe mineral is either ferromagnesian (dark

colored) or felsic (light colored

ferromagnesian (mafic) minerals rich in Fe, Mg – creates a dark colored

rocksPyroxene (Augite)Pyroxene (Augite)

Amphibole (hornblende)Amphibole (hornblende)Mica - BiotiteMica - Biotite

Igneous Rock Classification LabIgneous Rock Classification Lab

Igneous Rock Composition

Mineral composition = Mineral assemblages = ChemistryThe mineral is either ferromagnesian (dark colored) or felsic (light colored)

Felsic – mineral composition is light colored minerals

Igneous Rock Composition

Mineral composition = Mineral assemblages = ChemistryThe mineral is either ferromagnesian (dark colored) or felsic (light colored)

Felsic – mineral composition is light colored minerals

Ca-plagioclaseCa-plagioclase

K-feldspar (orthoclase)K-feldspar (orthoclase)

Mica- muscoviteMica- muscovite

QuartzQuartz

Ori

gin

Tex

ture

Intr

usi

ve

Ph

ane-

riti

c

Very coarse crystal grains, usually allgrains are approximately the same sizew/ respect to each other. Grains> one inch

A mosaic of coarse-grains that areeasily visible to the unaided eye – grainsgreater than 1 mm

Gra

nit

e

Gra

no

-d

iori

te

Dio

rite

Gab

bro

Per

ido

tite

GranitePegmatite

MaficPegmatite

Rh

yoli

te

Dac

ite

An

des

ite

Bas

alt

X

Ext

rusi

ve

Fine to very fine grains, usually to smallto be distinguished with the unaidedeye or even with a hand lensA

ph

an-

itic

Gla

ssy

Po

r-o

us

Fra

g-

men

tal

Obsidian

Pumice Scoria

RhyoliticTuff

BasalticTuff

80%

40%

20%

Glassy – non-crystalline, non-granularColor varies between black and brown

Highly vesicular, finely crystalline to glassyPumice (light), Scoria (dark)

Composed of fragments of all sizesProduced in volcanic environments, AshPartially re-fused or cemented

Ver

yC

oar

se

Rock Descriptions

Igneous Rock Classification Felsic Mafic

Sedimentary Rock Identification LabSedimentary Rock Identification Lab

Sandstone Arches

How is a sedimentary Rock formed???How is a sedimentary Rock formed???How is a sedimentary Rock formed???How is a sedimentary Rock formed???

Pre-existingPre-existingRockRock

Pre-existingPre-existingRockRock

ErosionErosionErosionErosion

Water, Wind, Water, Wind, IceIce

Water, Wind, Water, Wind, IceIce

Breaks downBreaks downPre-existing rockPre-existing rockBreaks downBreaks downPre-existing rockPre-existing rock

SedimentSedimentSedimentSediment

TransportedTransportedTransportedTransportedLakesLakesLakesLakes

RiversRiversRiversRivers

Depos

ited

Depos

ited

Depos

ited

Depos

ited

CompactedCompactedCementedCemented

CompactedCompactedCementedCemented

LithifiedLithifiedLithifiedLithified SedimentarySedimentaryRockRock

SedimentarySedimentaryRockRock

Why is the earth’s surface 75% sedimentary rocks?????????Why is the earth’s surface 75% sedimentary rocks?????????Why is the earth’s surface 75% sedimentary rocks?????????Why is the earth’s surface 75% sedimentary rocks?????????

Three major categories of Sedimentary Rocks

Clastic Sedimentary rocks

Chemical Sedimentary rocks

Bio-chemical (bio-clastic) Sedimentary rocks

Three major categories of Sedimentary Rocks

Clastic Sedimentary rocks

Chemical Sedimentary rocks

Bio-chemical (bio-clastic) Sedimentary rocks

Clastic (inorganic-detrital)rocks are composed of particles or grains. Rockname is dependent on grain size.

Decreasing grain size

Decreasing grain size2+ mm2+ mm

2 mm2 mm

1/16 mm1/16 mm

1/256 mm1/256 mm

Chemical Rocks – inorganic, non-clastic rocks that are commonly the result of evaporation and precipitation

Chemical rocks contain no fossils, or biological material but may react with HCl

Chemical Rocks – inorganic, non-clastic rocks that are commonly the result of evaporation and precipitation

Chemical rocks contain no fossils, or biological material but may react with HCl

The Great Salt Lake, Utahhalite (salt) crystals

The Great Salt Lake, Utahhalite (salt) crystals

Calcium Carbonate (CaCO3) chemical rocks (evaporation / precipitation processes)Calcium Carbonate (CaCO3) chemical rocks (evaporation / precipitation processes)

Chemically precipitated SiO2Chemically precipitated SiO2

Bio-chemical (bio-clastic, biogenic) rocks – result from animal and plant secretions. The term clasticindicates that these rocks contain fossils or parts of plantsshells, compacted plat material

Bio-chemical (bio-clastic, biogenic) rocks – result from animal and plant secretions. The term clasticindicates that these rocks contain fossils or parts of plantsshells, compacted plat material

Animal partsAnimal parts

Cemented shell fragmentsCemented shell fragments

Lithified plant materialLithified plant material

Classification ProcedureClassification Procedure

Step 1: Determine if the rock is clastic or non-clastic Step 1: Determine if the rock is clastic or non-clastic

Step 2: If the rock is clastic, determine the grain size and diagnostic properties. Make the ID.Step 2: If the rock is clastic, determine the grain size and diagnostic properties. Make the ID.

Step 3: If the rock is not clastic, determine if the rock is either chemical or bioclastic

chemical – will not contain particles such as grains and organic material. Test rock to observe fizzing (carbonates) Match diagnostic properties on chart for ID

bio-clastic- rock will be composed of particles that are organic- animal parts, plant secretions.

Test rock to observe fizzing (carbonate) Match diagnostic properties on chart for

ID

Step 3: If the rock is not clastic, determine if the rock is either chemical or bioclastic

chemical – will not contain particles such as grains and organic material. Test rock to observe fizzing (carbonates) Match diagnostic properties on chart for ID

bio-clastic- rock will be composed of particles that are organic- animal parts, plant secretions.

Test rock to observe fizzing (carbonate) Match diagnostic properties on chart for

ID

Metamorphic RocksMetamorphic Rocks

Meta (to change) morphic (form) = to change formMeta (to change) morphic (form) = to change form

Metamorphism– to change a rocks compositional and textural characteristics by subjecting the rock to various pressure/temperature relationships

Rocks undergo a solid-state-transformation

Metamorphism– to change a rocks compositional and textural characteristics by subjecting the rock to various pressure/temperature relationships

Rocks undergo a solid-state-transformation

The parent rock: represents the pre-existing rock metamorphism

Example: Shale (parent) Schist Limestone (parent) Marble

The parent rock: represents the pre-existing rock metamorphism

Example: Shale (parent) Schist Limestone (parent) Marble

Identification of Metamorphic RocksIdentification of Metamorphic Rocks

Identified by using the rocks Texture and CompositionIdentified by using the rocks Texture and Composition

Compositional characteristics – types of mineral presentcommon minerals: quartz, feldspar, muscovite

special minerals: talc, garnet, chlorite related to P/T relationships

Compositional characteristics – types of mineral presentcommon minerals: quartz, feldspar, muscovite

special minerals: talc, garnet, chlorite related to P/T relationships

Textural characteristics – minerals are oriented in various degrees of “parallelism”

platy sub-parallel parallel

Textural characteristics – minerals are oriented in various degrees of “parallelism”

platy sub-parallel parallel

Grain size distribution – fine-grain to coarse-grain reflects P/T relationshipsfine-grain coarse-grainLow P/T High P/T

Grain size distribution – fine-grain to coarse-grain reflects P/T relationshipsfine-grain coarse-grainLow P/T High P/T

FOLIATED

FOLIATED

Gneissic Schistose Slaty

Coarse-grainedHigh P/T

Fine-grainedLow P/T

Alternating lightand dark mineralbands

Alternating lightand dark mineralbands

Parallel to sub-parallelMineral alignmentParallel to sub-parallelMineral alignment

“compressed”layering - platy“compressed”layering - platy

Textural characteristicsTextural characteristics

Non-foliated texture – minerals are not visible and there orientation does not exist

Rock is composed of single type chemistry.

Non-foliated texture – minerals are not visible and there orientation does not exist

Rock is composed of single type chemistry.

NON-FOLIATEDNON-FOLIATED

Example: rocks composed of CaCO3

rocks composed of SiO2

Example: rocks composed of CaCO3

rocks composed of SiO2

Shows NO foliationComposed of ONE COMPOSITIONShows NO foliationComposed of ONE COMPOSITION

QuartzSiO2

QuartzSiO2

CalciteCaCO3

CalciteCaCO3

Plant MaterialC -carbonPlant MaterialC -carbon

How can oneTell the

Difference ?

How can oneTell the

Difference ?

“Fussed glass”Scratches glass

Hard H = 7

“Fussed glass”Scratches glass

Hard H = 7

“Sometimes xln”Fizzes in HCl

Soft H = 3

“Sometimes xln”Fizzes in HCl

Soft H = 3

Classification ProcedureClassification Procedure

Step 1:•Determine if the rock is foliated or non-foliated

•does the rock contain “parallelism” or grains•does the rock consist of a single chemistry with

no visible grains?

Step 1:•Determine if the rock is foliated or non-foliated

•does the rock contain “parallelism” or grains•does the rock consist of a single chemistry with

no visible grains?

Step 2:•If the rock is foliated

•examine the degree of “parallelism”•examine the grain-size distribution•refer to charts for ID

Step 2:•If the rock is foliated

•examine the degree of “parallelism”•examine the grain-size distribution•refer to charts for ID

Step 3:•If the rock is non-foliated

•determine the composition of the rock•determine the special characteristics•Refer to charts for ID

Step 3:•If the rock is non-foliated

•determine the composition of the rock•determine the special characteristics•Refer to charts for ID