Week 2 Flashcards
1
Q
how many minerals are known
A
almost 6000 (5327 officially)
2
Q
why study minerals
A
minerals are the building blocks of the body of our planet
- minerals make up all of the rocks and sediments on earth
minerals are important to humans
- industrial minerals (manufacturing)
- ore minerals (metals)
-gem minerals (human passions)
3
Q
what is a mineral
A
geologic definition:
- naturally occuring
- formed geologically
-solid
-crystalline structure
-most minerals are inorganic
4
Q
can we synthesize minerals
A
yes: sapphire, diamond, quartz
5
Q
how are minerals formed by geologic processes
A
mostly formed by geologic processes
- freezing from a melt (like volcanic magmas)
- precipitation from a dissolved state in water or other solvent
- chemical reactions at high pressures and temperatures
6
Q
how are minerals formed by biogenically
A
living organisms can create minerals
- vertebrate bones
- oyster mussel and clam shells
- skeletal types
- tooth enamel
7
Q
how are minals formed
A
- mostly geologic processes and also by living organisms ( biogenically)
8
Q
what is a crystalline structure
A
a state of matter that can maintain its shape indefinitely
9
Q
minerals can be melted or vapourized but they are not ….
A
liquids or gases..
10
Q
how are mineral defined?
A
by their structure butthey have a definite elemental composition
11
Q
minerals can be defined by a chemical formula but more commonly they are defined by
A
as a structure
12
Q
what are the different structures of a mineral
A
simple ( largely defined by a chemical formula)
complex (many elements might be substituted)
13
Q
what is a crystal
A
- single continuous piece of crystalline solid
- typically bounded by flat surfaces (crystal faces)
- crystal faces grow naturally as the minral forms
- crystals are sometimes prized mineral specimens
14
Q
T or F crystals come in a variety of different shapes
A
T
15
Q
what makes a crystal so special
A
- regular geometric from
- crystals interact with light to create attractive beauty
16
Q
what is X-ray diffraction used for
A
study and identify minerals
17
Q
how does X-ray diffraction worl
A
- X-ray beam passed through a crystal or crystal powder creates distinctive pattern
- diffraction pattern related to arrangement of atoms in crystal
18
Q
what do you see when you look inside a crystal
A
- ordere atomic patterns in minerals display symmetry
- ordered atoms like tiny balls packed together
- held in place by chemical bonds
19
Q
symmetry characterisitcs are used to what
A
identify minerals
20
Q
what are the displays of symmetry in crystals
A
- mirror images
- rotation about an axis (or axes)
21
Q
what defines the crystal structure q
A
the way atoms are packed
22
Q
what do the physical propreties (hardness, shape) depend upon
A
- identity of atoms
- arrangement of atoms
- nature of atomic bonds
23
Q
what does the nature of atomic bonds control caracteristics of crystals (chemical) ex:
A
ex: - diamond and graphite are both made of Carbon
- diamond: atoms arranged in tetrahedra: hardest mineral
- graphite: atoms arranged in sheets: softest mineral
24
Q
five ways minerals can form
A
- solidification from a melt
- precipitation from a solution
- solid-state diffusion
- biomineralization
- precipitating directly from a gas
25
fullerines and graphene
26
Solidification from a melt
- crystals grow when the melt cools
- liquid freezes to form solid
27
precipitation from a solution
seeds form when a solution becomes saturated
28
what are garnets
garnets are fundamentally a structure rather than a stoichiometric chemical composition as in molecules (reddish minerals)
29
what are the various compositions that the structure of the garnet can be formed with
X3Y2 (SiO4)
X is occupied by divalent cations (Ca, Mg, Fe, Mn)2+
Y is occupied by trivalent cations (Al, Fe, Cr)3+
30
mineral growth is often restricted by what
lack of space
ex: anhedral: grown in tight space, no cystal faces
Ex: euhedral: grown in an open cavity, good crystal faces
31
what is much more prevalent: anhedral or euhedral
anhedral
32
where do euhedral crystals grow
in the open space in a geode
33
how can minerals be destroyed ( cant destroy the chemistry)
- melting: heat breaks the bonds holding atoms together
- dissolving: solvents (moslty water) break atomic bonds
- chemical reaction: reactive materials break bonds
34
name some easily seen properties for mineral identification
color
crystal shape
35
some properties require handling or testing
- hardness
- magnetization
- specific gravity
36
common propreties
- color
- streak on ceramic tile
- luster
- hardness
- specific gravity
- crystal habit
- fracture or cleavage
37
color of minerals
part of visible light that is not absorbed by a minerla
- disgnostic for some minerals (ex: malachite is distinctive green)
- some mineras exhibit a borad color range ex: quartz
38
what does color varities reflect
trace impurities
39
what is streak
color of a powder produced by crushing mineral
obtained by scraping a mineral on unglazed porcelain
40
luster
the way a mineral surface scatters light
- metallic
-nonmetallic: silky, glassy,satiny, resinous, pearly, earthy
41
hardness
sscratching resistance of a mineral
derives from the strength of atomic bonds
hardness compared the Mohs scale for hardness
42
Mohs scale for hardness
fingernail: Gypsum
Copper penny: Calcite
Glass: Apatite
Stell File: Orthoclase
43
what does specific gravity represent
the density of a mineral: mineral weight over the weight of an equal water volume
(how heavy it feels)
ex: Galena feels heavier than quartz
44
crystal habbit
-a single crystal with well-fromed faces,
or
- an aggregate of many well-fromed crystals
- arrangement of faces reflects internal atomic structure
45
variation in directional growth rates
blocky or equand (equal growth rate in 3D
- bladed (shaped like knofe blade)
- needle-like: rapid growth in one dimension, slow in others
46
special physical propreties
- effervescence (reactivity with acid ex: calcite)
- magnetism (ex: magnetite0
- taste: (lick test ex: halite (salt))
47
fracture
mineral breaks in ways that reflect atomic bonding
48
what does fracturing imply
equal bond strength in all directions
ex: quartz displays conchoidal fracture
- break like glasss (smooth cruved surfaces)
- shard edges
49
cleavage
tendency to break along planes of weaker atomic bonds
50
what does cleavage produce in a mineral
flat and shiny surfaces
51
how is cleavage described
by the number of planes and their angles
52
T or F: crystal faces only occur on external surfaces and often forms parallel steps
T
53
Exemple of cleavage
- one direction (micas)
- two directions at 90º (ex pyroxene)
- two directions not at 90º (ex amphibole)
- three directions at 90º (ex: halite)
- three directions not at 90º (ex: calcite)
54
mineral classification: seperated how?
- the principal anion (negative ion)
OR
- anionic group (negative molecule)
55
what is the most abundant mineral class
silicates
56
Minerals are classified by their dominant anion
- silicates (SiO24-) are colled rock forming minerals
- constitute almost the entire crust and mantle of Earth
- they are the most common mineral
ex: quartz
57
mineral classes: - Oxides
- Metal Cations (FE2+, Fe3+, Ti2+) are bonded by oxygen
- ex: magnetite (Fe3O4), Rutile (TiO2), Hematite (fe2O3)
58
mineral classes: Sulfides (S)
- metal cations are bonded to a suflide anion
ex: - pyrite (FeS2)
- Galena (PbS)
- (sphalerite ZnS)
59
mineral classes: Sulfates (SO42-)
metal cation bonded to a sulfate anionic group
- many sulfates form by evaporation of seawater
- ex: Gypsum (CaSO4 X 2H2O) , Anhydrite (CaSO4)
60
mineral class: by their dominan anion: Halides (CL- or F-)
ex: halite (NaCl)
- Fluorite (CaF2)
61
mineral class: dominant anion: Carbonates (CO32-)
ex: Calcite (CaCO3)
Dolomite (Ca,Mg)(CO3)
Natrite (Na2CO3)
62
mineral class: minerals with no (dominant) anion: native metlas
common: (Cu, Au, Ag)
- ex: :Copper (Cu)
- gold (Au)
- Silver (Ag)
pure masses of single metal or alloy
63
where do silicate minerals dominate eath
mantle and crust
64
what are silicate minerals made out of
made of oxygen and silicon with other atoms
65
what is the anionic unit of SiO44- (silicate_
silicon-oxygen tetrahedron
- four O atoms are bonded to a central Si atom
- Define the corners of a four-sided geometric figure
- the "silica tetrahdron" is the building block of silicates
66
Independent Tetrahedra
- silica tetrahedra share no oxygens
- linked by cations
- ex: olivine, Garnet
67
Single Chains
silica tetrahedra link to share two oxygens
- ex: pyroxenes
68
double chains
silica tetrahedra alternate sharing two and three oxygens
- ex: amphiboles
69
sheet silicates
- silica tetrahedra share three oxygens
- create 2D flat sheets of linked tetrahedra
- characterized by one direction of perfect cleavage
- ex: micas, clays
70
Framework silicates
all four oxygens in each silica tetrahedron are shared
- ex: feldspars, silica (quartz) group
71
what is a gemstone
a mineral with special value
- rare: fromed by unusual geological processes
- beautiful: strikingly unique colour, clarity, luster
72
what is a gem
a cut and polished stone created for jewelry
- precious: stones that are particularly rare and expensive (ex: diamond, ruby)
- semiprecious: less rare (ex: topaz, garnet)
73
T or F gemstone facets are not natural crystal faces
True
74
where do diamonds come from
originate under extremely high pressure (150 km deep in the upper mantle) where pure carbon is compressed into the diamond structure
- rifting causes deep-mantle rock to move upward
- diamonds are found in kimberlite pipes
75
what is a volcano
a vent where molten rock comes out of earth
76
what happens when a volcano errupts
- hot basaltic lava pools around volcanic vent
- hot, syrupy lava runs downhill as a lava flow
- the lava flow slows, loses heat, crusts over
- flow stops and cools, forming igneous rock
77
how is igneous rock formed
by cooling from a melt
78
difference between magma and lava
magma: melted rock below ground
- lava: melted rock once it has reached the surface
79
what temp does igneous rock freeze at
high temp: 1100 to 650 degrees
80
different types of igneous rock
- extrusive igneous rock and intrusive igneous rock
81
extrusive igneous rocks
- cool quickly at the surface (above ground)
- lava flows, streams or mounds of cooled melt
- pyroclastic debris: cooled framgents
- volcanic ash: fine particles of volcanic glass
- volcanic rock: fragmented by eruption
82
intrusive igneous rocks
cool below the ground
- much greater volume than extrusive igneous rocks
- cooling rate is slower than extrusives (large colume magma chamber, smaller volume tabular bodies or columns)
83
why does magma form?
- magma is not eveywhere below earth's crust
- magma only forms in special tectonic conditions
84
what are the special tectonic conditions that magma forms in
- partial melting occurs in the crust and upper mantle
- magma is fluid-like rather thatn solid
- melting is caused by: pressure release, volatile addition, heat transfer
85
what are the causes of melting
- decrease in pressure (decompression)
- addition of volatiles ( lfux melting)
- heat transfer melting
86
decrease in pressure (P) decrompression (cause of melt)
- the base of the crust is hot enough to melt mantle rock
- due to high Pressure, rock deosnt melt
- melting will occur if pressure decreases
87
when does the pressure drop (melting of rock)
drops when hot rock is carried to shaller depths
- matnle plumes
- beneath rifts
-beneath mid-ocean ridges
88
addition of volatiles (cause of melting)
- volatiles lower the melting Temperature of a hot rock
- common volatiles include H2O and CO2
- subduction carries water into the mantle, melting rock
89
heat transfer melting (cause of melting)
-rising magma carries mantle heat with it
- this raises the T in nearby crustal rock, which then melts
90
what is magma made of?
magmas have three componens ( solid, liquid, gas)
- solid: solidified mineral crystals are carried inthe melt
- liquid: the melt itself is composed of mobile ions (majority Si and O, lesser Al, Ca, Fe, Mg, Na, K)
- different mixes of elements yield different magmas
-gas: variable amounts of dissolved gas occur in magma: dry magma (scarce volatiles) wet magma (15% volatiles ex: H2O)
91
types of magma
based on % of silica (SiO2)
- felsic (feldspar and silica 66-76%)
- intermediate (52-66%)
- mafic (Mg and Fe rich) (45-52% SiO2)
- ultramafic (38-45% SiO2)
92
why are there different magma compositions?
magma vary chemically
- source rock dictates initioal magma composition
- initial source rock compositions
-partial melting
-assimilation
-magma mixing
93
Partial melting
- upon melting, rocks rarely dissolve uniformly
- portion of rock melts instead: Si rich minerals melt first then Si poor minerals melt last
- partial melting yields a silica-rich magma
94
source rock dictates initioal magma composition ex:
- mantle source: ultra-mafic and mafic magmas
- crustal surface: mafic, intermediate, and felsic magmas
95
partial melting yields what type of magma
partial melting yields a silica-rich magma
96
what happens when you remove the partial melt from its source what is created
- felsic magmas form granites and rhyolites
- mafic magmas form basalts and gabbros
97
assimilation
magma melts the wall rock it passes through
- blocks of wall rock fall into magma
- assimilation of these rocks alters magma composition
98
magma mixing
- different magmas may blend in a magma chamber
- result combines the characteristics of the two
- often magma mixing is incomplete, resulting in blobs of one rock type suspended within the otehr
99
how does magma move
it tends to rise upward:
- magma may move upward in the curst
- may breach the surface: volcano
100
what does magma movement do
transfers mass from deep to shallow parts of earth:
- crucial process in the earth system
- provides the raw material for soil, atmosphere and ocean
101
why does magma rise
- it is less dense than surrounding rocks: (magma = more buoyant, which lifts it upward)
- weight of overlying rock creates pressure ( pressure squeezes magma upward)
102
what is the speed of magma movement and what does it depend on
the speed of magma flow is governed by viscosity
103
what does a lower viscosity do to magma dlow
eases movement
104
how is a lower viscosity magma generated
- higher T
- lower SiO2 content
- higher volatile content
105
temperature does what (viscosity of magma)
hot= lower viscosity
cooler = higher viscosity
106
volatile content (viscosity)
more volatiles = lower visc.
less volatiels = higher viscosity
107
silica content (viscosity)
less SiO2 ( mafic) ; lower viscosity
more SiO2 (felsic): higher viscosity
108
how fast does magma cool what does it depend on
- depth (depth is hotter, shallow is cooler)
-shape (spherical bodies cool slowly, tabular faster)
- groundwater: circulatin water removes heat
109
why d0es depth change cooling rate?
deep plutons lose heat very slowly: take long time to cool
- shallow flows lose heat more rapidly: cool quickly
110
how are igneous rocks changed
- changes with cooling:
fractional crystallization: early crystals settle by gravity
Melt composition changes as a result: Fe, Mg, Ca are removed as early mafic minerals settle out, remaining melt becomes enriched in Si, Al , Na and. K
111
what does Bowen's REaction Series do?
divsed experiments cooling melts:
- early crystal settle out, (removing Fe, Mg, Ca)
- remaining melt progressively enriched in Si, Al, Na
112
what did Bowen discover
minerals solidify in a specific series:
- continuous: plagioclase change from Ca rish to Na rich
- discontinuous: minerals start and stop crystallizing
113
ex of discontinuous minerals
olive
pyroxene
amphibole
biotite
114
