MineralsChapter 3

Naturally Occurring Minerals must occur

naturally. Cannot be man made. Cement, bricks, steel,

and glass all come from materials found in the earth, but these are made by people.

Inorganic Inorganic materials

were never living. Coal is made from

the remains of ancient plants and animals, so coal is not a mineral.

Minerals Naturally occurring Inorganic solid Crystal structure Definite chemical

composition

Solid The state of matter

when the material is below its freezing point.

Definite shape, definite volume.

Particles are fixed in place.

Crystal Structure The particles of the

material line up in a regular, repeating pattern.

Has flat sides called faces, that meet at sharp edges and corners.

Definite Chemical Composition Always contains certain

elements in the same proportion.

Almost all minerals are compounds, which are two or more different elements bonded together (holding hands).

Pyrite is two sulfur atoms holding hands with an atom of iron.

Chemical Formula’s Have a definite format. Written together means

they are bonded. Coefficients tell how

many of the whole thing you have.

Subscripts tell how many of the atom before it that you have.

So 2H means two separate hydrogen atoms.

H2 mean two hydrogen atoms holding hands.

H2O means two hydrogen atoms holding hands with an oxygen atom.

More Formula’s 2 H2O means you have

two separate water molecules, each containing two hydrogen and one oxygen atom.

Bornite is a copper ore that turns purple when exposed to air. It’s formula is Cu5FeS4.

So how many of each atom are present?

Five copper one iron four sulfur

Identifying Minerals Each mineral has

specific properties that can be used to identify it.

Hardness density luster color streak crystal system cleavage and fracture special properties

Hardness A measure of how

easily a mineral can be scratched.

Determined by the atomic structure of the mineral.

Friedrich Mohs developed the scale we use today.

Density Minerals will have a

certain density regardless of the size of the sample.

When geologists compare the weight of the mineral to the weight of an equal volume of water it is called specific gravity.

Color Not especially useful

in identifying minerals, as some minerals like quartz can come in a variety of colors.

Luster The way a mineral

reflects light. Can be metallic or

non-metallic. Shiny or dull. Earthy, waxy, pearly,

glassy.

Streak The color of its

powder. Not always the same

as the color of the mineral.

Pyrite has a gold color, but its streak is a greenish black.

Gemstones

Gemstones are highly valued for their beauty and rarity, than for their usefulness.

Important gemstones include diamond, sapphire, ruby, emerald, aquamarine, topaz, and tourmaline.

RocksChapter 4

Rocks are: A solid made of one or

more minerals and other materials.

Classifying Rocks Rocks are classified based on how they were

formed.

Identifying Rocks Rocks are further identified by: color texture mineral composition

Types of Rock

Click below to watch the Visual Concept.

Visual Concept

Section 1 The Rock CycleChapter 4

Texture

Texture is the quality of a rock that is based on the sizes, shapes, and positions of the rock’s mineral grains.

Composition Composition is the chemical makeup of a rock.

Composition can describe either the minerals or other materials in the rock.

Grains Particles of minerals

that make up a rock. Texture is determined

by grain size, grain shape, and grain pattern.

Grain Size Some rocks have

grains that are large and easy to see.

These rocks are coarse grained.

Other rocks have grains so small they are microscopic.

These are fine grained rocks.

Grain Shape Grains can be: fine sand crystals fragments that can be

smooth or jagged

Grain Pattern Grains can lie flat in

layers like a stack of pancakes.

Some have patterns that look like waves or swirls

Some resemble rows of beads.

Others will have random patterns.

No Visible Grain Some rocks resemble

pieces of glass. These rocks cooled

very quickly so crystals did not have time to grow.

Mineral Composition Since rocks are really

combinations of minerals, geologists must slice their samples into very thin pieces to test which minerals are present.

Origin of Rocks Rocks are classified by

the way they are formed. Igneous rocks: formed

from the cooling of molten rock.

Sedimentary rocks: formed from sediments being compacted and cemented.

Metamorphic rocks: existing rock that is changed by heat, pressure, or chemical reactions.

Igneous Rocks

Identified by origin, texture, and mineral composition.

From the Latin word “ignis,” which means fire.

Tend to have average densities.

Extrusive Igneous Rock Extrusive rock is

formed from lava that erupted on the surface and rapidly cooled. Will have tiny crystals, be very fine grained, and sometimes even appear glassy.

Basalt is most common of this type.

Basalt Forming

Intrusive Igneous Rock Forms when magma

cools underground. Usually cools slowly,

so it will have large crystals and be coarse grained.

Granite is most common intrusive rock.

Large Crystals Lava at the surface

cools quickly, so crystals do not have time to grow.

Rock is a good insulator, so rock cooling underground takes much longer. So intrusive rock will have larger crystals.

Explain This! How would you explain

an intrusive rock that had both large and small crystals?

Right! It must have cooled slowly at first, then cooled more rapidly as it got closer to the surface.

Porphyritic Rock These rocks look like

Jell-O with fruit mixed in.

Deep underground the heat cannot dissipate as rapidly, so the rock cools slowly. Near the surface the heat can escape into the air, so it cools rapidly.

Felsic Igneous Rock Lighter colored

igneous rocks will have lots of silica.

They tend to be less dense than the darker versions.

Mafic Igneous Rock Less silica means

these rocks will be darker than their felsic counterpart.

They will be denser also.

Little silica →→→→→→→→→→→→ lots of silica

Sill Slab of volcanic rock

that squeezes between rock layers.

Tend to be horizontal.

Dike

Slab of volcanic rock that cuts across rock layers.

Tend to be vertical.

Batholith

A very large mass of volcanic rock that form deep underground.

Can cover several states in the USA.

Stone Mountain might be part of an exposed batholith.

Stock Smaller area of volcanic rock than a batholith Stone Mountain might be a stock that is

exposed.

Sedimentary Rocks Formed from particles

of sediment deposited by wind and water.

Sediment is small pieces of solid materials that come from rocks or living things.

Origins of Sedimentary Rock

Wind, water, ice, sunlight, and gravity all cause rock to physically weather into fragments.

Through erosion, these rock and mineral fragments, called sediment, are moved from one place to another.

The sediment is deposited in layers, and eventually newer layers cover the older layers.

Section 3 Sedimentary RockChapter 4

Sedimentary Rock Cycle

Click below to watch the Visual Concept.

Visual Concept

Question? What do these rocks

have in common?

Stratification Yes, all these rocks

are layered or “stratified.”

Forming Sedimentary Rock

Weathering The process by which

exposed rock is broken down into small pieces by the elements of nature (wind, rain, ice, chemical actions, plants, etc.)

Erosion Occurs when water or

wind loosens rock and soil and carries it away.

Deposition The process by which

the sediment settles out of the water or air carrying it.

Sediment is deposited when the wind or water slows down.

Compaction As the sediments settle they will loosely fit on top of

each other. As the years go by, more and more sediment is added. The bottom layers get compacted by the weight of the

layers above them.

Cementation While compaction is

going on, minerals in the rock slowly dissolve.

The dissolved minerals seep into the spaces between the compacted sediment.

They crystallize and glue the sediments together.

Lithification The process by which

sediment becomes sedimentary rock.

From Greek word “lithos,” which means rock.

Erosion Deposition Compaction Cementation

Types of Sedimentary Rocks Clastic: formed when

rock fragments are squeezed together.

Organic: (biological) formed from the remains of living things.

Chemical: formed when dissolved minerals crystallize.

Clastic Sedimentary Rock

Shale Clastic rock formed

from tiny particles of clay.

Water deposits tiny clay particles in thin layers.

Feels smooth and splits easily into flat sheets.

Sandstone Formed from sand on

beaches, ocean floors, river beds, and deserts.

Mainly quartz. Lots of small holes

between the grains, so it will absorb water.

Conglomerate and Breccia Formed from a mixture

of rock fragments of different sizes.

Conglomerate has rounded edges.

Breccia has larger fragments with sharp or jagged edges.

Breccia

Organic Sedimentary Rocks Formed from the

remains of plants and animals that were deposited in thick layers.

Also called biological rock.

Coal Formed from the

remains of ancient swamps.

As layer upon layer of dead plants built up, the bottom layers were compacted into coal.

Stored chemical energy from the sun.

Fossil fuel.

Coal Pictures

Limestone Formed from the

shells of ancient sea animals and plants.

Shells fall to the bottom of the ocean in layers, some 100’s of meters thick.

Compaction creates limestone.

Chalk Formed from the

shells of ancient sea life.

Creates layers 100’s of feet thick

White Cliffs of Dover

Chalk Cliffs

Chemical Sedimentary Rocks Formed when water

with dissolved minerals evaporates.

The left behind minerals will crystallize.

Gypsum Made from calcium

deposits. Used to make sheet

rock for homes.

Halite Rock salt Formed from seas and

oceans that dried up. The salt forms large

crystals.

Metamorphic Rocks “Meta” is ancient

Greek for change. “Morphosis” is ancient

Greek for form. Metamorphic rock

then is rock that has changed from one form to another.

Origins of Metamorphic Rock Metamorphic rocks are rocks

in which the structure, texture, or composition of the rock have changed. All three types of rock can be changed by heat, pressure, or a combination of both.

A rock’s texture or mineral composition can change when its surroundings change. If the temperature or pressure of the new environment is different from the one in which the rock formed, the rock will undergo metamorphism.

Contact Metamorphism Contact Metamorphism When

magma moves through the crust, the magma heats the surrounding rock and changes it.

Some minerals in the surrounding rock are changed into other minerals by this increase in temperature.

The greatest change occurs where magma comes into direct contact with the surrounding rock.

Regional Metamorphism Regional metamorphism

occurs when pressure builds up in rock that is buried deep below other rock formations, or when large pieces of the Earth’s curst collide with each other.

The increased pressure and temperature causes rock to become deformed and chemically changed.

Section 4 Metamorphic Rock

How Metamorphic Rocks Form Deep below the Earth’s

surface the intense heat and pressure can change rocks.

Their appearance, texture, crystal structure and mineral content can change.

Fossils will be destroyed.

Almost melted! Metamorphic rocks are

often squished, smeared out, and folded.

Despite these uncomfortable conditions, metamorphic rocks do not get hot enough to melt, or they would become igneous rocks!

Classifying Metamorphic Rock Classified by the

arrangement of the grains.

Foliated Non-foliated Usually harder and

denser than the rock they come from.

Texture of Metamorphic Rock

All metamorphic rock has one of two textures.

Foliated Metamorphic Rock

Non-foliated Metamorphic Rock

quartzite

gneiss

Foliated Metamorphic Rock Grains are in

parallel layers or bands.

“Foliated” is the Latin word for leaf.

Describes the thin layering found in many metamorphic rocks.

These rocks will split along these bands.

Slate Formed when shale is

subjected to pressure. Denser, more

compacted than shale. Produces flat plates

when broken.

Slate to Schist If slate is subjected to

even greater pressure and moderate temperatures, schist is formed.

Granite to Gneiss Granite becomes

gneiss when subjected to heat and pressure.

The atoms end up lining up in bands.

Non-foliated Metamorphic Rock

Mineral grains are randomized.

Amorphous Do not split into

layers. Usually smoother and

denser than the parent rock.

Quartzite Occurs when

sandstone is compressed by pressure.

Usually very hard.

Marble Formed from

metamorphosed limestone.

Much harder and denser.

Foliated Metamorphic

The Rock Cycle