Chapter 3 ROCKS ... and how to identify them

Chapter 3ROCKS ... and how to

identify them

Chapter 3ROCKS ... and how to

identify them

Mr. Litaker

This is your cue to advance to the next slide.This is your cue to advance to the next slide. (*)(*)

THE ROCK CYCLETHE ROCK CYCLERocks are naturally occurring combinations of Rocks are naturally occurring combinations of

minerals, fossils or other hard materials. minerals, fossils or other hard materials. They are classified by the way in which They are classified by the way in which they they formform. The three rock types are: . The three rock types are: igneousigneous, , sedimentarysedimentary and and metamorphic.metamorphic.

All rocks on Earth are locked into a system of All rocks on Earth are locked into a system of cycling and re-cycling known as the cycling and re-cycling known as the ROCK ROCK CYCLECYCLE. (*). (*)

METAMORPHICMETAMORPHIC SEDIMENTARYSEDIMENTARY

IGNEOUSIGNEOUS

weathering, transportation, lithification

heat, pressure, ions

THE ROCK CYCLETHE ROCK CYCLE

(*)(*)

11stst stage stage

MagmaMagma

Cooling & Cooling & CrystallizationCrystallization Weathering Weathering

& & ErosionErosion

Cementation &Cementation &

CompactionCompaction

IgneousIgneous

SedimentarySedimentaryMetamorphicMetamorphic

S E D I M E N T SS E D I M E N T S

IGNEOUS ROCKSIGNEOUS ROCKSIGNEOUS ROCKSIGNEOUS ROCKS are are ““born of fireborn of fire”. In other ”. In other words, they were words, they were once molten and once molten and upon cooling, theupon cooling, the magmamagma (molten rock) (molten rock) crystallized into solid crystallized into solid rock. Igneous rocks rock. Igneous rocks may form deep inside may form deep inside the Earth or at the the Earth or at the Earth’s surface when Earth’s surface when a volcano erupts. a volcano erupts. (*)(*)

magma

conduit

Anatomy of a Vol cano

vent lava

land surface

IGNEOUS ROCKSIGNEOUS ROCKSSloooow cooooling rate !

deep beneathdeep beneath the Earth’s the Earth’s surface allows crystals to surface allows crystals to grow to large size.grow to large size.

These crystals are easily These crystals are easily visible and distinguish this visible and distinguish this group of igneous rocks as group of igneous rocks as INTRUSIVE Igneous RocksINTRUSIVE Igneous Rocks..

(INSIDE)(INSIDE)

Rapid coolingRapid cooling near or at the near or at the Earth’s surface, produces Earth’s surface, produces many small crystals that many small crystals that are not readily seen by the are not readily seen by the unaided eye. unaided eye.

This group of igneous rocks This group of igneous rocks is calledis called EXTRUSIVE EXTRUSIVE Igneous Rocks Igneous Rocks and are and are typically volcanic in origin. typically volcanic in origin. Cooling may be so rapid Cooling may be so rapid that crystals do not have a that crystals do not have a chance to form and instead chance to form and instead a a glass is produced. (*)glass is produced. (*)

L I G H T C O L O R E D F e l s i c

I N T E R M E D I A T E C O L O R E D

D A R K C O L O R E D M a f i c

V E R Y D A R K C O L O R E D U l t r a m a f i c

C O A R S E - G R A I N E D

( Y o u c a n s e e d i f f e r e n t

m i n e r a l s )

G R A N I T E : C a n s e e c r y s t a l s . U s u a l l y g r a y o r p i n k . C a n s e e q u a r t z - g r a y , g l a s s y g r a i n s . C a n s e e f e l d s p a r - p i n k , b u f f , o r w h i t e .

D I O R I T E : C a n s e e c r y s t a l s w i t h s o m e w h a t m o r e l i g h t c o l o r e d f e l d s p a r g r a i n s t h a n d a r k c o l o r e d m i n e r a l s . A m i x o f l i g h t a n d d a r k b u t w i t h n o q u a r t z . S a l t & p e p p e r a p p e a r a n c e .

G A B B R O : C a n s e e c r y s t a l s — l o t s o f f l a t s h i n y c l e a v a g e s u r f a c e s . U s u a l l y b l a c k t o g r e e n i s h b l a c k .

F I N E - G R A I N E D

( Y o u c a n N O T s e e c r y s t a l s , f o r

t h e m o s t p a r t )

R H Y O L I T E : U s u a l l y g r a y , p i n k , p a s t e l . M i g h t s e e s m a l l c l e a r , r e c t a n g u l a r c r y s t a l s . S o m e t i m e s b a n d e d .

A N D E S I T E : L i g h t t o d a r k g r a y . N o r m a l l y h a s s m a l l b l a c k c r y s t a l s

B A S A L T : U s u a l l y b l a c k o r r u s t r e d . M a y h a v e s o m e o r l o t s o f g a s b u b b l e h o l e s , s o m e h o l e s m a y b e f i l l e d . M a y s e e s m a l l g r e e n g r a i n s .

G L A S S Y

O B S I D I A N : B l a c k , r e d , g r e e n , G L A S S

P E R L I T E : U s u a l l y p e a r l y g r a y . M a y c o n t a i n A p a c h e T e a r s .

P U M I C E : L O T S o f g a s b u b b l e h o l e s , v e r y l i g h t w e i g h t , w i l l f l o a t o n w a t e r . A b r a s i v e .

P O R P H Y R I T I C

( 2 g r a i n s i z e s )

A L L C R Y S T A L L I N E I G N E O U S V A R I E T I E S m a y e x h i b i t p o r p h y r i t i c t e x t u r e

F R A G M E N T A L

T U F F : C o m p a c t e d v o l c a n i c f r a g m e n t s g e n e r a l l y l e s s t h a n 4 m m d i a m e t e r ( a s h )

V O L C A N I C B R E C C I A : M i x e d t u f f a n d a n g u l a r l a r g e ( > 3 2 m m d i a m e t e r ) f r a g m e n t s

A G G L O M E R A T E : M i x e d a s h a n d r o u n d e d / s u b - r o u n d e d l a r g e ( > 3 2 m m d i a m e t e r ) f r a g m e n t s

P E R I D O T I T E : C o m p o s e d o f 9 0 -1 0 0 % o l i v i n e P Y R O X E N I T E : C o m p o s e d o f p r e -d o m i n a t e l y p y r o x e n e

A M P H I B O L I T E : C o m p o s e d o f p r e -d o m i n a t e l y a m p h i b o l e s ( s u c h a s h o r n b l e n d e )

C L U E S T O I G N E O U S R O C K S

C O L O R

T E X T U R E

(*)(*)

Granite - intrusiveGranite - intrusiveGRANITEGRANITE is a coarse to is a coarse to medium-grained rock that medium-grained rock that forms from the cooling of forms from the cooling of magma deep within the magma deep within the Earth Earth ((intrusiveintrusive).).

It is made up mainly of varying It is made up mainly of varying amounts of the minerals:amounts of the minerals: **quartz,quartz,**feldspar (orthoclase),feldspar (orthoclase), **muscovitemuscovite, , **biotitebiotite and and*hornblende*hornblende. .

quartz

feldspar

biotite mica

(*)(*)

(*)(*)

Granite - intrusiveGranite - intrusive

Pegmatite

Graphic Granite

Porphyritic

mica

feldspar

Granite - intrusiveGranite - intrusivePegmatitePegmatite a Special Case

tourmaline

feldsparfeldspar

mica

quartzquartz

PEGMATITESPEGMATITES are classified as are classified as intrusive intrusive igneous rocks, igneous rocks, but there is a but there is a difference. difference.

They are VERY They are VERY coarse coarse grained!!!grained!!!

Diorite - intrusiveDiorite - intrusive

DIORITEDIORITE is very similar is very similar to granite, but is to granite, but is distinguished in the distinguished in the hand specimen by the hand specimen by the absence of visible absence of visible quartz.quartz.

Generally it has aGenerally it has a salt salt and and pepper pepper appearance appearance (about ½ black(about ½ black and ½ and ½ white).white).

feldspar biotite (*)

Gabbro - intrusiveGabbro - intrusiveGABBRO is a coarse-grained is a coarse-grained rock that is high in iron & rock that is high in iron & magnesium-bearing magnesium-bearing minerals (pyroxenes, minerals (pyroxenes, amphiboles or hornblendeamphiboles or hornblende, , plagioclase feldsparplagioclase feldspar, , olivineolivine). ).

The rocks will be The rocks will be darkdark in in color, somewhat heavier color, somewhat heavier than granitic rocks and than granitic rocks and NOOOO quartz.NOOOO quartz.

Black minerals are primarily amphibole (like hornblende) and plagioclase

feldspar. (*)(*)

Peridotite -Peridotite - intrusiveintrusivePeridotite -Peridotite - intrusiveintrusive

PERIDOTITEPERIDOTITE or or DUNITEDUNITE is is composed of 90-composed of 90-100% olivine. As a 100% olivine. As a result it is result it is characteristically characteristically olive-green in color.olive-green in color.

This material is thought to This material is thought to have originated in the have originated in the upper mantle of the Earth. upper mantle of the Earth. (*)(*)

Rhyolite – extrusiveRhyolite – extrusiveRHYOLITERHYOLITE’S name comes from

the Greek rhyo, from rhyax, “stream of lava”. WHITE color

It is formed when molten rock It is formed when molten rock with the same composition as a with the same composition as a high silica granite oozes high silica granite oozes (rhyolite is VERY viscous and (rhyolite is VERY viscous and does not really flow) to the does not really flow) to the Earth’s surface; and therefore Earth’s surface; and therefore coolscools quickly quickly so only so only microscopic-sized crystals microscopic-sized crystals develop. VERY FINE GRAINEDdevelop. VERY FINE GRAINED

The volcanoes that The volcanoes that produce rhyolite are produce rhyolite are very explosive varieties very explosive varieties such as Mt. St. Helens, such as Mt. St. Helens, Krakatoa and O’Leary Krakatoa and O’Leary Peak (AZ). Frequently it Peak (AZ). Frequently it is banded due to flow is banded due to flow alignment of differentalignment of different associated minerals associated minerals (quartz(quartz, , feldsparfeldspar, , micamica,, andand hornblende hornblende). ). (*)(*)

This is an example of This is an example of banded rhyolite. (*)banded rhyolite. (*)

Rhyolite – extrusiveRhyolite – extrusive

If you look closely, you might see tiny clear phenocrysts of If you look closely, you might see tiny clear phenocrysts of feldspar. (*)feldspar. (*)

This is another sample of rhyolite. This is another sample of rhyolite. This has a crystal of garnet that This has a crystal of garnet that grew after the rhyolite was grew after the rhyolite was deposited. (*)deposited. (*)

Andesite - extrusiveAndesite - extrusive

ANDESITEANDESITE is the fine-is the fine-grained equivalent of grained equivalent of DIORITE. It tends to be DIORITE. It tends to be a darker gray than a darker gray than rhyolite and is often rhyolite and is often porphyritic, with visible porphyritic, with visible hornblende. hornblende.

hornblende hornblende phenocrystsphenocrysts

(*)(*)

Basalt - extrusiveBasalt - extrusive

BASALTBASALT occurs as thin to occurs as thin to massive lava flows, massive lava flows, sometimes accumulating sometimes accumulating to thicknesses of to thicknesses of thousands of feet and thousands of feet and covering thousands of covering thousands of square miles. The square miles. The volcanoes that produce volcanoes that produce basaltic lavas are relatively basaltic lavas are relatively quiet, such as the Hawaiian quiet, such as the Hawaiian Islands volcanoesIslands volcanoes. Basalt. Basalt

is dark, fine-grained and often is dark, fine-grained and often vesicularvesicular (having gas (having gas pockets). The pockets may be pockets). The pockets may be filled with secondary minerals, filled with secondary minerals, e.g. quartz, zeolite minerals, e.g. quartz, zeolite minerals, calcite, opal, etc. and then it is calcite, opal, etc. and then it is called called amygdaloidalamygdaloidal (a-mig-(a-mig-duh-duh-loyloy-dal) basalt.-dal) basalt.

The name may have originated The name may have originated with Pliny who used the with Pliny who used the Ethiopian word Ethiopian word basal basal for iron-for iron-bearing rocks. (*)bearing rocks. (*)


Gases released near the Gases released near the surface of a lava flow create surface of a lava flow create bubbles or bubbles or vesiclesvesicles that are that are “frozen” in stone. (*)“frozen” in stone. (*)

Vesicular (Scoria)

Amygdaloidal

Volcanic Bomb (*)

(*)(*)


Peridotite (*)

Peridotite xenolith

Basalt (*)


Pahoehoe Pahoehoe is a is a feature that forms on feature that forms on the surface of very the surface of very fluid basalt flows. fluid basalt flows. Much like the skin on Much like the skin on a bowl of tomato a bowl of tomato soupsoup – the surface in – the surface in contact with the air contact with the air begins to crystallize, begins to crystallize, while the fluid lava while the fluid lava below continues to below continues to flow. This drags the flow. This drags the upper, still plastic, upper, still plastic, surface into a series of surface into a series of smooth wrinkles.smooth wrinkles. (*) (*)

Basalt – ExtrusiveBasalt – Extrusive

The Bottom The Bottom side of this side of this pahoehoe is pahoehoe is rough and rough and jagged and jagged and is called is called Aa.Aa.

Obsidian - extrusiveObsidian - extrusiveOBSIDIANOBSIDIAN is volcanic glass is volcanic glass

(an acrystalline “solid” (an acrystalline “solid” –actually a –actually a supercooled supercooled liquidliquid). Its ). Its glassy, lustrous and glassy, lustrous and sometimes banded sometimes banded appearance makes it appearance makes it rather easy to rather easy to distinguish from all distinguish from all other rocks.other rocks. It is It is composed of the composed of the elements that make elements that make quartz, feldspar and iron/ quartz, feldspar and iron/ magnesium mineralsmagnesium minerals that that

have cooled so quickly that the minerals could not develop and crystallize.

Colors vary from black to red, black & red (mahogany), gray, green, iridescent, snowflake.

Apache Tears are little nodules of obsidian.

Obsidian - extrusiveObsidian - extrusiveFlow banding

Apache tear

Snowflake

Perlite - extrusivePerlite - extrusive

PERLITEPERLITE is a light gray volcanic glass, having numerous concentric cracks which give rise to a perlitic or onion skin structure. It is generally of rhyolitic composition. It also exhibits a pearly luster.

Apache Tears are some times found embedded in perlite.

Apache Tear

Pumice - extrusivePumice - extrusivePUMICEPUMICE is highly is highly vesicular (i.e. it has vesicular (i.e. it has lots of gas bubble lots of gas bubble holes) and is of holes) and is of rhyolitic rhyolitic composition.composition.

Due to the many Due to the many small holes, it is small holes, it is lightweight and will lightweight and will often float in water.often float in water.Created by Created by VOLCANIC ASHVOLCANIC ASH

Tuff - extrusiveTuff - extrusive

Tuff is the accumulation of ash and small pyroclastic debris (<4mm). Thick beds may form for many miles around a very explosive volcano, such as Mt. St. Helens.

Often, when the material is still hot upon deposition, it welds into a very hard rock.

Volcanic Breccia - extrusiveVolcanic Breccia - extrusive

VOLCANIC BRECCIA VOLCANIC BRECCIA is pyroclastic (fire-formed fragments) and forms in explosive eruptions. It is a mix of large angular fragments and small ash.

Often, the material is hot when it comes to rest and cools (welds) into a very hard rock.

http://www.ees.nmt.edu/Geol/classes/geol101/lec8/L8_sedrx.ppt.htmhttp://www.ees.nmt.edu/Geol/classes/geol101/lec8/L8_sedrx.ppt.htm

SEDIMENTARY ROCKSSEDIMENTARY ROCKSSEDIMENTARY ROCKSSEDIMENTARY ROCKSSED. ROCKS are composed of particles SED. ROCKS are composed of particles

derived from pre-existing rocks or by derived from pre-existing rocks or by the crystallization of minerals that the crystallization of minerals that were held in solutionswere held in solutions. .

A general characteristic of this group is the A general characteristic of this group is the layering or layering or stratificationstratification, , as seen in the as seen in the outcropoutcrop. . A layer of exposed rock (cliff).A layer of exposed rock (cliff).

Sedimentary rocksedimentary rocksSedimentary rocksedimentary rocks

Sedimentary rocks that are composed edimentary rocks that are composed of particles of pre-existing rocks are of particles of pre-existing rocks are considered considered FRAGMENTALFRAGMENTAL or or CLASTICCLASTIC.. These fragments show These fragments show evidence of transport – rounding of the evidence of transport – rounding of the grains and size sorting.grains and size sorting.

sedimentary rockssedimentary rockssedimentary rockssedimentary rocksCHEMICACHEMICALL sedimentary rocks are sedimentary rocks are

the result of either precipitation of the result of either precipitation of solids from solutions (like salt from solids from solutions (like salt from water) or by organic process, like water) or by organic process, like shells from marine organisms.shells from marine organisms.

Mostly Silicate MineralsMostly Silicate Minerals

C L U E S T O S E D IM E N TA R Y R O C K S

F R A G M E N T A L : C o m p o s e d o f p ie c e s o f ro c ks a n d m in e ra ls

L A R G E P IE C E S (B o u ld e rs ,c o b b le s ,

p e b b le s )

B R E C C IA : C o m p o s e d o f la rg e a n g u la r p ie c e s a n d c la y C O N G L O M E R AT E : C o m p o s e d o f la rg e ro u n d e d p ie c e s a n d c la y

S M A L L P IE C E S (s a n d )

S A N D S T O N E : L o o ks s a n d y (m a y “s h e d ” s a n d g ra in s ) , fe e ls ro u g h ( l ike s a n d p a p e r) ; m a y b e ta n , w h ite , re d , g ra y.

V E R Y S M A L L P IE C E S (c la y, s i l t, m u d )

S H A L E : H a s ve r y th in la ye rs ; o fte n b la c k. M a y h a ve fo s s ils — u s u a ll y im p re s s io n s (n o s h e ll, b u t in d e n ta tio n w ith p a tte rn o f s h e ll) o r c a rb o n ize d fi lm (as fo r p la n ts ) . H a s a d u ll lu s te r . Is s o ft. W h e n ta p p e d w ith a ro d o r o n a ta b le , i t g e n e ra ll y m a ke s a d u ll th u n k. SSILTSTONEILTSTONE – Made of the mineral silt – Made of the mineral silt

Breccia – fragmental or ClasticBreccia – fragmental or Clastic

A BRECCIABRECCIA is made of made of varying sizes of varying sizes of angularangular fragments cemented fragments cemented together.together. The name is The name is from the Italian word for from the Italian word for “broken stones” or “broken stones” or “rubble”. “rubble”.

Many form as the result of fault movement; others form as the result of rapid and short transportation, such as landslides.

Conglomerate - fragmentalConglomerate - fragmentalCONGLOMERATESCONGLOMERATES are

very similar to breccias, but the fragments are the fragments are roundedrounded.. The name The name is from the Latin is from the Latin conglomeratusconglomeratus for for “heaped, rolled or “heaped, rolled or pressed together”.pressed together”.

These rocks form in alluvial fans, stream beds and pebble beaches.

Sandstone - fragmentalSandstone - fragmentalSANDSTONE SANDSTONE is made up is made up

of fine-grained particles of fine-grained particles (1/16 –2 mm). The sand (1/16 –2 mm). The sand grains (often quartz) are grains (often quartz) are commonly cemented by commonly cemented by silica, carbonates, clay or silica, carbonates, clay or iron oxides.iron oxides. Sandstone is identified by its sandy texture – which often translates into a gritty feel.

Environments in which sandstones form include beaches, sand bars, deltas and dunes.

Coconino Sandstone, the result of a Permian age coastal dune field

Shale - fragmentalShale - fragmentalSHALESHALE is a very common rock very common rock

made of silt and clay sized made of silt and clay sized particles. It is generally particles. It is generally very thin-bedded and splits very thin-bedded and splits along the bedding planes.along the bedding planes.

Normally gray to black, shale Normally gray to black, shale may be brown to dark red, may be brown to dark red, depending on the amount of depending on the amount of included iron oxide.included iron oxide.

Shale forms in quiet environ-ments, such as lakes, swamps, deltas and offshore marine.

Black shale, deposited in a offshore basin in a Middle Cambrian sea. Wheeler Shale with trilobite fossil (Elrathia kingii)

Fish scales

Utah

M O R E C L U E S T O S E D IM E N TA R Y R O C K S

C H E M IC A L : R o c k s a re c rys ta l l in e

L IM E S T O N E S : C o m p o s e d o f c a lc i te a n d a l l W IL L F IZ Z vig o ro u s ly in a c id C rys ta l l in e — L o o k s s u g a r y, u s u a l ly g ra y o r ta n F o s s il i fe ro u s — C o n ta in s s e a s h e lls (u s u a lly) o r o th e r a q u a tic o rg a n is m s T ra ve r t in e — L o o k s s u g a r y w ith b a n d s o f v a r io u s c o lo rs C h a lk — W h ite a n d s o ft ( c o m e s o ff o n h a n d s ) C o q u in a — C o n ta in s a lm o s t n o th in g b u t s e a s h e l ls o r s e a s h e l l fra gm e n ts

C H E R T: C ry p to c ry s ta llin e Q U A R T Z V e r y f in e — c a n N O T s e e c rys ta ls W a x y lu s te r C o n c h o id a l fra c tu re (b re a k s l ik e g la s s ) V e r y h a rd — w i l l e a s ily s c ra tc h g la s s M a y b e A N Y C O L O R (R e d = J a s p e r , B la c k = F l in t, in c lu d e s S i l ic i f ie d W o o d )

G Y P S U M : W h ite , g ra y, c le a r V e r y s o ft — yo u c a n s c ra tc h w ith f in g e rn a i l C le a r s h e e ts , f ib ro u s o r s u g a ry

R O C K S A LT: W h ite to c le a r — c u b ic s h a p e S o ft — y o u c a n s c ra tc h i t w i th f in g e rn a i l T a s te s l ik e ta b le s a l t ( IT IS T A B L E S A L T !)

C O A L : B la c k ; B r i t t le ; L ig h tw e ig h t M a y c o n ta in p la n t fo s s i ls V a r ie tie s : p e a t, l ig n i te ( in c l . je t) , s u b -b i tu m in o u s , b i tu m in o u s

D IAT O M IT E : W hite V e r y s o ft ( c o m e s o ff o n y o u r h a n d s ) L ig h tw e ig h t W i ll N O T fiz z in H C l a c id (u n l ik e c h a lk )

Limestone - chemicalLimestone - chemical

LIMESTONE LIMESTONE is composed is composed primarily of calcite. primarily of calcite. Generally it is dense, Generally it is dense, fine-grained, and usually fine-grained, and usually white to dark gray. Its white to dark gray. Its most distinguishing most distinguishing feature is its solubility in feature is its solubility in weak hydrochloric or weak hydrochloric or acetic acid accompanied acetic acid accompanied by brisk effervescence.by brisk effervescence.

****

The environment The environment of deposition is of deposition is generally warm, generally warm, shallow seas. shallow seas. Therefore, marine Therefore, marine invertebrate fossils invertebrate fossils are commonly are commonly trapped in this rock.trapped in this rock.

Uses:Uses: Manufacture of lime and Portland cement & to Manufacture of lime and Portland cement & to neutralize smokestack gases. neutralize smokestack gases.

Finely ground, used as a functional filler in Finely ground, used as a functional filler in products such as paint, countertops & plastics. products such as paint, countertops & plastics.

The dust on chewing gum is ground The dust on chewing gum is ground limestone. limestone.

Mild abrasive additive to toothpaste. Mild abrasive additive to toothpaste.

Soil conditioner Soil conditioner

Flux in processing iron and copper ores. Flux in processing iron and copper ores.

Building and ornamental stone.Building and ornamental stone.

LIMESTONE - chemicalLIMESTONE - chemical

Redwall LimestoneRedwall Limestone

Pleistocene, Rocky Point,Pleistocene, Rocky Point,

CrystallineCrystalline

FossiliferousFossiliferous

CoquinaCoquina

Travertine Mayer, AZ

MexicoMexico

CHERT - chemicalCHERT - chemical

CHERT CHERT is crypto-crystalline is crypto-crystalline quartz. It is often the quartz. It is often the result of the dissolution of result of the dissolution of volcanic ash and is volcanic ash and is sometimes found in sometimes found in extensive beds, such as extensive beds, such as the novaculite of the novaculite of Arkansas.Arkansas.

Chert can be any color, but Chert can be any color, but extensive beds are extensive beds are generally white to gray.generally white to gray.

GYPSUM - chemicalGYPSUM - chemical GYPSUMGYPSUM (calcium sulfate) is (calcium sulfate) is

found in geographically wide-found in geographically wide-spread deposits resulting from spread deposits resulting from the evaporation of a body of the evaporation of a body of water, such as ocean basin or water, such as ocean basin or playa lake.playa lake.

It is soft (H=2) & usually white to gray. Three varieties are: Alabaster, Satin Spar and Selenite.

Gypsum Gypsum is mined for use in is mined for use in wallboard and plasters, as an wallboard and plasters, as an agricultural amendment and to agricultural amendment and to control the set/cure time of control the set/cure time of Portland cement.Portland cement.

AlabasterSatin Spar

Selenite

Gypsum & Anhydrite (water-less Gypsum & Anhydrite (water-less calcium sulfate), Carlsbad, NMcalcium sulfate), Carlsbad, NM

ROCK SALT - chemicalROCK SALT - chemical

ROCK SALTROCK SALT (halite – (halite – sodium chloride) is also a sodium chloride) is also a deposit resulting from deposit resulting from evaporation of a marine evaporation of a marine basin or playa lake.basin or playa lake.

It has cubic cleavage and It has cubic cleavage and tastes salty.tastes salty.

Rock salt Rock salt is used as a is used as a source of chlorine and source of chlorine and sodium, as a food sodium, as a food supplement, in water supplement, in water softeners and as a road softeners and as a road de-icer.de-icer.

Halite Trona, CA

COAL - chemicalCOAL - chemical

COALCOAL is considered a rock, is considered a rock, although it is not composed of although it is not composed of minerals, but rather the minerals, but rather the decomposed remains of large decomposed remains of large volumes of vegetation that volumes of vegetation that accumulated in a wet, low accumulated in a wet, low oxygen environment, such as oxygen environment, such as a swamp or marsh.a swamp or marsh.

Peat, Lignite and Sub-Bituminous Peat, Lignite and Sub-Bituminous & Bituminous& Bituminous are sedimentary are sedimentary varieties of coal and are used varieties of coal and are used as fuels.as fuels.

Coal (sub-bituminous) out of the Coal (sub-bituminous) out of the Cretaceous Dakota Formation of Cretaceous Dakota Formation of north-eastern Arizona.north-eastern Arizona.

METAMORPHIC ROCKSMETAMORPHIC ROCKS

METAMORPHIC ROCKSMETAMORPHIC ROCKSMETAMORPHIC ROCKSMETAMORPHIC ROCKSMETAMORPHIC ROCKSMETAMORPHIC ROCKS have changed ( have changed (metameta) their form () their form (morphicmorphic). ).

Under the influence of heat, pressure and fluids, pre-existing Under the influence of heat, pressure and fluids, pre-existing rocks are changed in form and even in internal atomic structure rocks are changed in form and even in internal atomic structure to produce new rocks stable at the new conditions. to produce new rocks stable at the new conditions. ********** This is This is donedone withinwithin thethe solidsolid statestate, i.e. , i.e. without meltingwithout melting. .

Changes that occur include: Changes that occur include: increase in grain sizeincrease in grain size, , new mineralsnew minerals andand foliation foliation (parallel alignments). (parallel alignments).

1. Metamorphic rocks that exhibit 1. Metamorphic rocks that exhibit parallel alignments of minerals parallel alignments of minerals

are calledare called FOLIATEDFOLIATED.. In In these rocks, the minerals all line these rocks, the minerals all line up perpendicular to the exerted up perpendicular to the exerted pressure.pressure.

2. Metamorphic rocks 2. Metamorphic rocks composed of minerals that composed of minerals that are not elongated or flat, are not elongated or flat, do not exhibit parallel do not exhibit parallel alignments and are calledalignments and are called NON-FOLIATEDNON-FOLIATED..

FOLIATED: Rocks have layers or banding

SLATE: Rock breaks into very thin layers Beginning to look polished; Is harder than shale Cannot see crystals Black , gray or red

PHYLLITE: Like slate, but shinier (“phyllitic sheen” — similar to satin)

SCHIST: Very shiny — you can SEE CRYSTALS (usually MICA) Is layered May have crystals (of garnet, tourmaline, etc.) growing with the mica

GNEISS: Crystalline Black & White BANDING (due to segregation of minerals)

CLUES TO METAMORPHIC ROCKS

SLATE - foliatedSLATE - foliated

SLATE is derived from SLATE is derived from shale.shale.

It is a dense, microcrystalline It is a dense, microcrystalline rock, but one in which parallel rock, but one in which parallel planes are very evident in its planes are very evident in its slaty foliation – a feature slaty foliation – a feature resulting from the alignment resulting from the alignment of clay and mica of clay and mica minerals,which allows it to minerals,which allows it to split readily into sheets. It split readily into sheets. It may be gray, black, green or may be gray, black, green or red.red.

Uses include roofing, flagstone, Uses include roofing, flagstone, pool table tops and pool table tops and “blackboards”.“blackboards”.

Note the relatively dull luster of slate.

PHYLLITE - foliatedPHYLLITE - foliated

PHYLLITEPHYLLITE

is somewhat more is somewhat more metamorphosed than slate.metamorphosed than slate.

The platy crystals of mica have The platy crystals of mica have grown and the rock displays grown and the rock displays a subtle, satiny shine a subtle, satiny shine referred to as referred to as “phyllitic“phyllitic sheen”.sheen”.

The name comes from its leaf-The name comes from its leaf-like (many fine layers) like (many fine layers) appearance.appearance. Note the phyllitic Note the phyllitic

sheen.sheen.

SCHIST -SCHIST - foliatedfoliatedSCHIST -SCHIST - foliatedfoliatedSCHISTSCHISTis medium to coarse-grained, is medium to coarse-grained,

crystalline, with prominent crystalline, with prominent parallel mineral orientation. parallel mineral orientation. Typically, it is predominately Typically, it is predominately muscovite mica, which lends muscovite mica, which lends a silvery white to gray a silvery white to gray sparkly appearance.sparkly appearance. It is not It is not unusual for accessory minerals unusual for accessory minerals (such as garnets, staurolite, (such as garnets, staurolite, tourmaline) to grow in the rock.tourmaline) to grow in the rock.

Schist is added to clay mixtures Schist is added to clay mixtures as a strengthening material in as a strengthening material in vitreous pipe (red sewer) and vitreous pipe (red sewer) and clay roof tiles.clay roof tiles.

Crumpling of schist due to pressure and collapse of mica crystals

garnet garnet porphyroblastporphyroblast

tourmaline porphyroblast – note alignment

GNEISS - foliatedGNEISS - foliatedGNEISS GNEISS formed under formed under

conditions of high conditions of high temperatures and temperatures and pressures at great depth pressures at great depth during regional during regional metamorphism. It is metamorphism. It is characterized by characterized by foliation expressed as foliation expressed as black and white banding. black and white banding. Because the rock Because the rock becomes plastic, the becomes plastic, the banding is often banding is often contorted (squiggly).contorted (squiggly).

Gneissic granite – separation of dark & light minerals is just beginning

Well banded gneiss

Augen Gneiss

Augen = quartz pebble resistant to compression

kink in gneiss

Shale

metamorphism of shalemetamorphism of shaleSHALE is the most common sedimentary rock.

Through the agents of metamorphism it changes to rocks that are stable at higher temperatures and pressures.

These changes take place in the solid state.

Increasing Temperature and PressureIncreasing Temperature and Pressure

Slate Phyllite

SchistSchist Gneiss

GRANITEGRANITE

MELTING ProducesMELTING Produces

GRANITEGRANITE

METAMORPHICMETAMORPHIC SEDIMENTARYSEDIMENTARY

IGNEOUSIGNEOUS

mel

ting

heat

, pre

ssur

e,

ions

weathering, transportation

lithification

melting

weathering, transportation, lithification

heat, pressure, ions

THE ROCK CYCLETHE ROCK CYCLE

CLUES TO METAMORPHIC ROCKS

NON-FOLIATED: Shows NO layers or banding

MARBLE: Sugary looking Will fizz in HCl (acid) Often is multi-colored, may be white Soft — will not scratch glass

QUARTZITE: Very dense MAY look a bit sandy Very hard — will easily scratch glass

METACONGLOMERATE: Looks like sedimentary conglomerate, BUT it is harder (BREAKS THROUGH PEBBLES) and often the pebbles are squished & aligned (it is at this point foliated)

SERPENTINITE: Composed of members of the serpentine family (includes chrysotile asbestos) Generally light greenish gray to greenish black Waxy luster Often exhibit curved and slickensided surfaces

MARBLE – non-foliatedMARBLE – non-foliatedMARBLEMARBLE is metamorphosed

limestone or dolomite. The colors can vary from pure white to gray, green, yellow, brown, black, red or any combination thereof, depending on the ‘impurities’ in the parent limestone. Bands or streaks result from plastic flow during extreme deformation, due to high pressure and temperature.

It is calcite or dolomite and will fizz in weak acids.

Marble is used for building facades, floors, countertops, statuary, landscaping, paving/roofing, poultry grit, and as filler/extender for paint, plastics, paper and adhesives.

Aguila, AZ

Hewitt Canyon, AZ

QUARTZITE – non-foliatedQUARTZITE – non-foliated

QUARTZITEQUARTZITE is metamor-phosed quartz sand-stone. It is a very dense,durable, massive, microcrystalline rock (but still may retain a slightly sandy look). It can be any color, but tends to be white, tan or pink.

SERPENTINITE – non-foliatedSERPENTINITE – non-foliated

SERPENTINITESERPENTINITE is composed of one or more minerals in the serpentine family. It is common where wet basalts or mantle rocks are metamorphosed, such as at convergent boundaries.

Its green colors, waxy luster, often associated asbestos and common slickensided surfaces are clues to its identity.

Chrysotile asbestos

Salt River Canyon, AZ

METACONGLOMERATE – non-foliatedMETACONGLOMERATE – non-foliated

METACONGLOMERATE METACONGLOMERATE is metamorphosed conglomerate. It retains its pebbly appearance, but while a sedimentary conglomerate will break around the pebbles, a metaconglomerate will break through the pebbles.

If temperatures are high enough in the presence of pressure, the pebbles may become squished or flattened and will be elongated parallel to each other (becomes foliated).

ConglomerateConglomerate

High-Grade MetamorphismHigh-Grade Metamorphism

Considered Low-Grade metamorphismConsidered Low-Grade metamorphism

Documents

Chapter 3 ROCKS ... and how to identify them