chapter 20: rocks and minerals

our earth is an interconnected system that can be organized into “spheres”—name three

geosphere

hydrosphere

atmosphere

true or false

each sphere is separate but each sphere touches and is interconnected to the other spheres

true

the __________ is the rocks and minerals that make up our planet, and their relationship to Earth’s internal and external process

a) geosphere

b) hydrosphere

c) atmosphere

a) geosphere

the ___________ includes Earth’s fresh water—rivers, glaciers, and grounwater—and Earth’s saline water—the oceans

a) geosphere

b) hydrosphere

c) atmosphere

b) hydrosphere

the ________ envelops our planet and gives Earth its weather and climate

a) geosphere

b) hydrosphere

c) atmosphere

c) atmosphere

the elements that make up earth are found in its?

rocks and minerals

these rocks and minerals form earth’s what three parts?

crust, mantle, and core

the crust ride atop ____________ that move in response to heat flow and convection in earth’s interior

plate tectonics

a rock is created and deformed as the?

plates move and earth’s surface changed

as rock at earth’s surface is touched by water and air, it begins to?

erode and weather until its broken into smaller rocks; the process continues as the three spheres interact to influence landforms at Earth’s surface

what is the ground beneath our feet?

earth’s geosphere

geosphere is made up of rocks, and rocks are made up of ___________

minerals

the size and type of materials in a metamorphic rock can reveal the?

rate of crystallization and the conditions of formation (the temperature and pressure) that occurred deep below earth’s surface

what are the building blocks of rocks, and elements?

minerals

how many known elements are there?

about 100

out of the about 100 elements we have, it may surprise you to learna that just _______ elements make up 98% of earth’s entire mass

eight

all the other elements combined (other than the main eight) make up the remaining what percrcent of earth’s entire mass?

2 percent

true or false

earth’s elements are distributed evenly

false; earth’s elements are not distributed evenly

true or false

most of earth’s iron is concealed deep in the planet’s interior where it forms the central core

true

lighter elements, such as silicon and oxygen, are mostly distributed in the

a) inner-mid portions of the planets

b) mid-outer portions of the planets

c) outer portions of the planet

b) mid-outer portions of the planet

true or false

when first formed, the elements were distributed evenly throughout because is the way they accumulated

true

with each collision, heat was released because of the conversion of kinetic energy to heat energy—_____________

impact heating

as earth grew, gravitational attraction toward the planet’s center attracted even more debris. the attraction became strong enough that the young earth actually

a) enlarged itself which produced even more heat

b) squeezed itself into a smaller volume, which produced even more heat

c) stayed the same

b) squeezed itself into a smaller volume, which produced even more heata

a third source of heat came from the decay of naturally occurring, widely distributed?

radioactive elements

what are the three sources of heat?

impact heating

gravitational contraction heating

radioactive decay heating

what did the three sources of heat do for the young earth?

it brought young earth to its melting point

so in a molten or nearly molten state and under the influence of gravity, dense, heavy iron-rich material

a) sank into earth’s center and less dense, silicon and oxygen-rich material rose to the surface

b) sank into earth’s center, and more dense, silicon and oxygen-rich material rose to the surface

a) sank into earth’s center and less dense, silicon and oxygen-rich material rose to the surface

does density segregation happen in a mixture of oil and water like the earth’s materials?

yes

true or false

the heavier water sinks to form a layer at the bottom and the less-dense oil rises to form a layer at the top

true

in earth, density segregation led to the formation of a dense, iron-rich _______, a less-dense, rocky ______, and an even less dense, rocky ______

a) mantle; crust; core

b) core; crust; mantle

c) mantle; crust; core

d) core; mantle; crust

d) core; mantle; crust

when you compare the composition of the crust to that of earth as a whole you see what?

you see that the same few elements appear in both

the percentages however are quite different

the crust is composed of mostly

a) heavier elements

b) lighter elements

c) equally both

b) lighter elements

almost half the mass of earth’s crust is the element oxygen (o) and about a fourth is the element silicon (Si)

Checkpoint:

Earth’s interior is separated into layers, much as oil and vinegar in salad dressing separate into their respective layers. what caused this to happen?

Gravity; heat from collision impacts, gravtiational contraction, and radio-active decay softened our planet to a point at which its components could easily move around. in this state, dense elements sank toward earth’s center and lighter elements migrated upward to the surface

Checkpoint:

How is the composition of the whole earth different from that of earth’s crust?

Iron makes up one-third of Earth as a whole, but most of this iron is in Earth’s interior. Oxygen and silicon dominate Earth’s outer layers. And as we will soon see, this is why the most common group of rock-forming minerals—the silicate group—is dominated by these two elements

in everyday usage, we consider _________ as part of our diet, and _______ provide the raw materials needed for industry

minerals

a __________ is a naturally formed, inorganic, crystaline solid, composed of an ordered arrangement of atoms with a specific chemical composition

mineral

to be ___________ __________ means that it is not manufactured in a laboratory

naturally formed; so cubic zirconia and other synthetic gems are not minerals

___________ means that it is not made frmo materials that were onc partof a living thing

inorganic

is coal made from decayed plant material considered a mineral?

no because it is not naturally formed

to be a ____________ means that the atoms that make up a mineral are always arranged in an orderly geometric pattern

crystalline solid

glass is a solid. is it considered a crystalline solid?

no; it has no crystal structure

something like glass that has no crystal structure. it is _________ and so is not a mineral.

amorphous

true or false

the same types of minerals always have the same geometric arrangement of atoms

true

a specific chemical composition means that, for two samples to be considered the same mineral, they must have?

the same basic chemical composition

true or false

minerals typically don’t have a range of compositions

false; they do but its fixed with some limits

Checkpoint:

are synthetic diamonds minerals?

no; to be a mineral it has to be naturally formed

Checkpoint:

Obsidian is a kind of glass formed in volcanoes. is it a mineral?

no; obsidian, though naturally formed and has a specific range of chemical compositions, is a type of glass and is amorphous and so does not have a crystalline structure. it does not meet ALL the criteria to be considered a mineral

Minerals are classified by?

chemical composition (which elements are present) and crystal structure (how the elements are arranged)

true or false

a mineral’s observable physical properties depend on its outer microscopic properties

false; depend on its inner microscopic properties

true or false

micrscopic properties such as composition, crystal structure, and teh strength of chemical bonds determine a mineral’s crystal form, hardness (resistance to scratching), fracture or clevage (how a minerak breaks), color, and density

true

most minerals can be identified by easily observable?

physical properties

what are some other physical properties that can help identify minerals?

luster (the way a mineral reflects light)

streak (the color of a mineral in its powdered form)

a crystal’s shape, or ________, is an expression of the orderly arrangement of its atoms

crystal form

when you look at a fully formed crystal, what you see is?

the actual arrangement of atoms in its structure

true or false

each type of mineral has a unique composition and crystal form

true

are well-shaped crystals rare?

yes; they are rare in nature because of space constraints—most crystals grow in cramped spaces

some minerals have the same combinations of elements, but their atoms are arranged differently, which makes them?

different minerals

different architecture using the same materials can result in very?

different minerals

true or false

sometimes, two or more minerals contain the same elements in the same proportions, but their atoms are arranged differently

true; as a result, their crystalline structure and the properties they display are different

polymorphs mean?

poly = many morph = form

when minerals may contain the same elements and same proportions but their atoms are arranged differently

graphite and diamond are _______ because they both consist entirely of the same element, carbon, but the carbon atoms are arranged differently

polymorphs

because the formation of these similar-yet-different materials depends on ________ and _________, a polymorph is a good indicator of the geological conditions at the time and place of its formation

temperature; pressure

Checkpoint:

Many minerals can be identified by their physical properties—crystal form, hardness, fracture, cleavage, luster, color, streak, and density. Why is identifying a mineral by its crystal form usually difficult?

Well-shaped crystals are rare in nature because minerals typically grow in cramped spaces

Checkpoint:

What is a crystal?

a solid that has a crytalline structure—the atoms, ions, or molecules within it are arranged in a definite repeating pattern

true or false

hardness does not refer to its resistance to scratching. it refers to how easily a material breaks

false; hardness doesn’t refer to how easily a mineral breaks, but rather its resistance to scratching

for example, a quartz crystal can scratch a feldspar crystal because quartz is harder than feldspar

what are the measures of hardness?

the ability of one material to scratch another

the resistance of a mineral to being scratched

we use the _____________ to compare the hardness of different minerals

mohs scale of hardness

hardness depends on the strength of a mineral’s ___________

chemical bond

the stronger a mineral’s bonds, the

a) softer the mineral

b) the harder the mineral

b) the harder the mineral

the factors that influence bond strength are ?

ionic charge

atom or ion size

packing

strong bonds are generally found between

a) highly charged ions

b) slightly charged ions

c) low charged ions

d) charge doesn’t matter; its about packingg

a) highly charged atoms

the greater the attraction between ions, the

a) weaker the bond

b) stronger the bond

b) stronger the bond

small atoms and ions can generally pack

a) less than large atoms and ions

b) more than large atoms and ions

b) more than large atoms and ions

true or false

closely packed atoms and ions have a smaller distance between one another, and thus they form stronger bonds because they attract one another with more force

true

gold with its large atoms is

a) hard

b) soft

b) soft;

its atoms are rather loosely packed and loosely bonded

diamond with its small carbon atoms and tightly packed structure is

a) soft

b) hard

b) hard

the hardest mineral known

if you shatter the mineral calcite with a hammer, the surfaces where it broke are smooth and flat. this clean type of breakage occurs parallel to a mineral’s ________________—planes along which chemical bonds are weak or few in number

planes of weakness

____________ is the tendency for a mineral to break along such planes of weakness

clevage

cleveage planes are determined by?

crystal structure

chemical bond strength

true or false

some minerals show a greater tendency toward clevage than others

true

in general, minerals that have strong bonds between planar (flat) crystal surfaces show _______ clevage, wheras those with weak bonds along planar surfaces show more ________ clevage.

a) poor; distinct

b) distinct; poor

a) poor; distinct

the minerals muscovite (mica) and calcite both have

a) less-defined cleavage

b) well-defined cleavage

b) well-defined cleavage

muscovite cleaves where its bounding ______—between is planar sheets

a) strong

b) weak

b) weak

the atoms within the individual sheets are connected by ________ bonds, but between the sheets, the bonds are ______

a) strong; weak

b) weak'; strong

a) strong; weak

minerals that have no planar alignment of bonds, like quartz, cannot display cleavage and always _______

fracture

a fracture that is smooth and curved, so that is resmebles broken glass, is called?

conchodial

true or false

the minerals quartz and olivine display rough conchoidal fractures

false; they represent smooth conchoidal fractures

true or false

most minerals fracture regularly

false; most minerals fracture irregularly

Checkpoint:

When pieces of calcite and fluorite are scraped togeter, which scratches which?

looking at the table, fluorite is harder so therefore, fluorite would scratch calcite

Checkpoint:

the mienral muscovite displays very distinct cleavage, yet the mineral quartz fractures. how does this relate to each minerals’s crystal structure?

muscovite forms as a layered sheetlike structure. the bonds ebtween the different layers are weaker than the bonds within the the individual layers. its minerals cleave between the layers.

quartz is more complicated with no layering and no planes of weakness. therefore, quartz fractures.

true or false

although color is an obvious feature of a mineral, it is not a reliable means of identification

true

some minerals (copper and turquoise) have a distinctive color

true or false

most minerals either occur in a variety or colors or can be colorless

true

true or false

chemical impurities in a mineral do not affect color

false; it does

_________ is the color of a mineral in its powdered form

streak

true or false

although different smaples of the same mineral can have different colors, the color of the mineral’s streak is always the same

true

_______ can be used for identifying materials that have a metallic or semi-metallic luster

streak

minerals that do not have a metallic luster generally leave behind a _______ streak, which is not useful for identification

white

________ is a property of all matter, minerals included

density

________ of a mineral tells us how heavy a mineral feels for its size

density

gold particularly has a

a) low density

b) high density

b) high density