Review of Minerals What are the four characteristics of a mineral? Naturally Occurring Crystalline...

Review of Minerals

What are the four characteristics of a mineral?

• Naturally Occurring• Crystalline Solid• Specific Chemical Composition• Inorganic

Review of Minerals What mineral is

this?

DOLOMITE


this?

QUARTZ


this?

GALENA


this?

OLIVINE


this?

ORTHOCLASE FELDSPAR


this?

HEMATITE


this?

FLOURITE


this?

GYPSUM


this?

PYROXENE - AUGITE


this?

PYRITE


this?

MAGNETITE


this?

MUSCOVITE


this?

CALCITE


this?

HALITE


this?

GARNET


this?

AMPHIBOLE - HORNBLENDE


this?

BIOTITE

Goals for this labGoals for this lab Learn the basics of rock identification Learn how to distinguish between 3

rock types Observe hand samples and infer how

they might have been formed

*Solid aggregate of mineral grains, mineral crystals, or other rocks

*Some exceptions**Obsidian is made of volcanic

glass**Coal is made of plant fragments

*The materials forming rocks come from the Earth’s mantle as magma, from space, from organisms, or from the breakdown of other rocks and minerals.

*Environmental changes and processes affect the rock forming materials and existing rocks *These changes and processes produce 3 distinct groups of rocks

**IGNEOUS**SEDIMENTARY**METAMORPHIC

Igneous Rocks…Igneous Rocks…

What is an igneous rock?What is an igneous rock? Crystalline or glassy rocks formed from

the cooling and solidification of molten magma (below Earth’s surface)/lava (on Earth’s surface)

Compose the majority of the earth

Can use the texture and mineralogy of these rocks to determine where in the Earth they formed

Igneous Rock TexturesIgneous Rock Textures

Where the rock forms in the Earth and how quickly it cools determines what kind of texture it will have

Cooling Rates and Igneous Cooling Rates and Igneous TexturesTextures

The slower the crystals form, the larger they will be.

Deep = Hot = Slow Cooling= Large Crystals = Phaneritic Shallow = Cooler = Fast Cooling = Small Crystals =

Aphanitic Cooled slowly and then abruptly brought near surface and

cooled quickly = both large and small crystals = Porphyritic

Cooled extremely quickly = Glassy Cooled quickly and bubbles present = Vesicular Explosive welding of materials from volcanism =

Pyroclastic/Fragmental

Igneous Rock TexturesIgneous Rock TexturesGlassy

Vesicular

Pyroclastic/Fragmental

What minerals are present also What minerals are present also determine what kind of Igneous Rock determine what kind of Igneous Rock

forms.forms.

Chemistry changes Chemistry changes influence rock typeinfluence rock type

Minerals in Igneous Rocks Minerals in Igneous Rocks Cont.Cont.

Chemistry changes influence rock typeChemistry changes influence rock type

Mineralogy cont.Mineralogy cont. Felsic rocks

• dominated by K-feldspar, Na Plagioclase, quartz, and biotite• usually light in color• typical of continental crust (Granite and Rhyolite)

Intermediate rocks• dominated by plagiocase, amphibole, pyroxene, biotite, quartz• intermediate color• Andesite and diorite

Mafic rocks• Dominated by Ca-Plagioclase, pyroxene, olivine, amphibole• Usually dark in color• Typical of oceanic crusts (and the Moon, Mars, and Venus!) (Basalt, • Gabbro)

Ultramafic rocks• Dominated by olivine, minor amounts of pyroxene and Ca-

plagioclase• Rarely seen on Earth’s surface• Major constituent of Earth’s Mantle • Peridotite

Sedimentary Rocks…Sedimentary Rocks…

IGNEOUSMelting of rocks

SEDIMENTARYWeathering anderosion ofExposed rocks

Type of rock and

source material

Rock-formingprocess

ExampleCrystallization

Deposition,burial, andlithification

SedimentsSediments

Grain Size

Gravel >2mm

Sand 1/16-2mm

Silt 1/256-1/16mm

Clay <1/256

Sediments cont.Sediments cont.How are size and angularity affected by transport?

Sediments cont.Sediments cont.Grain Sorting

Sedimentary RocksSedimentary Rocks Formed by surface processes Sediments are formed from

weathering and erosion• Weathering = chemical and physical

processes that break up rocks into fragments of various sizes

• Erosion = set of processes that loosen soil and rock and move them

Sedimentary RocksSedimentary Rocks Loose sediments form sedimentary rocks

through the process of lithification Lithification = converts sediment into solid

rock by• Compaction = grains are squeezed together by

weight of overlying sediment into a mass denser than original

• Cementation = minerals precipitate around deposited particles and bind them together

Sedimentaryrocks

Metamorphicrocks

Plutons

DesertPlayalake

DeltaGlacier

The sedimentary stages of the rock cycle

Weatheringbreaks downrocks.

Erosion carriesaway particles.

Transportation moves particles downhill.

Deposition occurs when particles settle out or precipitate.

Diagenesis lithifies the sediment to make sedimentary rocks.

Burial occursas layers of sediment accumulate.

Sedimentary Rock TextureSedimentary Rock Texture Step 1 in identifying a Sedimentary

Rock• 3 types

Detrital/Siliclastic – rock made of fragments of other rocks

Biochemical/Bioclastic – composed of organically derived material

Chemical – sedimentary rocks precipitated out of solution

Step 2 in Identifying Sedimentary Rocks

Detrital Rocks

Oil and gas

Organic Matter

Coal

Pressure

Heat to90° - 120° C

Heat to90° - 120° C

Bioclastic Rocks

Chemical rocksChemical rocks

Evaporation Precipitation

Breccia Chert

ConglomerateCoal-Anthracite

Hematite

Limestone

Sandstone

Rocksalt

Shale

Siltstone

Metamorphic Rocks…Metamorphic Rocks…

MetamorphismMetamorphism Metamorphism is the solid-state

transformation of a protolith (parent or pre-existing rock) into texturally or mineralogically distinct new rock as the result of high temperature, high pressure, or both.

Metamorphism is Described by Texture, Index minerals, Grade, and

Facies

Identifying Metamorphic Identifying Metamorphic RocksRocks

Step 1• Determine the rock textureFoliated textures – rocks exhibit foliation…layering or parallel alignment of platy or flat mineral crystals (if the rock appears layered, it is foliated) due to pressure and recrystallization

Nonfoliated textures – rocks exhibit no layering, yet they may exhibit stretched fossils or long, prismatic crystals that have grown parallel to the pressure field

FoliationFoliation

Determined by the degree of • Cleavage• Schistosity• Banding

Increasing intensity of metamorphism

Increasing crystal size

Increasing coarseness of foliation

Low grade Intermediate grade High grade

Diagenesis Low grade Intermediategrade

High grade

Slaty RockCleavage

PhylliteTexture

Schistosity(abundantmicaceousminerals)

Gneissic Banding(fewer

micaceousminerals)

Migmatite

very flat foliation

scaly glitterylayer of visibleplaty mineralsand/or linearalignment of

long prismaticcrystals

alternatinglayers or

lenses of light and dark

medium to coarse grained

minerals

Banding

Foliated rocks are classified by the degreeof cleavage, schistosity, and banding.

wavy orwrinkled

foliation offine grained

minerals givingrock metallic

luster

Progression of metamorphism

Slate

Phyllite Schist

Start with a shale and then hitit with pressure and heat.

You end up with something that is really Gneiss!

Pre

ssu

re (

kilob

ars

)

Temperature (°C)

Dep

th (

km

)

LowGrade

IntermediateGrade

HighGrade

Increasing metamorphic grade

Slate

Phyllite

Schist

Blueschist Gneiss

Migmatite

Metamorphic Rock Textures(Unfoliated Textures)

- Crystalline Texture – medium to coarse grained aggregate of intergrown, equigranular, visible crystals (example: Marble)

- Microcrystalline Texture – fine grained aggregate of intergrown microscopic crystals (example: hornfels)

- Sandy Texture – medium to coarse grained aggregate of fused, sand-sized grains that resemble sandstone (example: quartzite)

- Glassy Texture – homogeneous texture with no visible grains or other structures and breaks along glossy surfaces (anthracite coal)


Step 2• Determine the rock’s mineralogical composition

and/or other distinctive properties Other Distinctive Features to Note Stretched or Sheared Grains – deformed pebbles, fossils, mineral crystals, that have been stretched, shortened, or sheared

Porphyroblastic Texture – arrangement of large crystals (PORPHYROBLASTS) set in a finer-grained groundmass (sort of sounds like porphyritic texture)

Hydrothermal Veins – fractures filled by minerals that precipitated from hydrothermal fluids

With increasing metamorphicgrade, mineral compositionchanges.

Mineral suites definemetamorphic facies.


Step 3• Use Five Step Chart for Metamorphic Rock

Analysis to determine the name of the rock you are identifying

Step 4• Based on the name of the identified

metamorphic rock, name the rock it was before metamorphism (this is the metamorphic rocks “parent” rock or protolith)

Sandstone: Quartzite, Metaquartzite

Shale: Slate

Phyllite

Schist

Gneiss

Limestone: Marble

Metamorphism of Sedimentary Rocks

Protolith

Metamorphism of Igneous Rocks

For most purposes, just put “meta” in frontof the protolith name.

Examples: metabasalt metarhyolite

If a mafic or intermediate metamorphic rock isdominated by amphibole and feldspars:

-Amphibolite

Review of Minerals What are the four characteristics of a mineral? Naturally Occurring Crystalline...

Documents

Transcript of Review of Minerals What are the four characteristics of a mineral? Naturally Occurring Crystalline...