Minerals Flashcards
1
Q
5 requirements of a mineral
A
- Solid
- Naturally occurring
- Fixed chemical composition
- Crystalline structure
- Inorganic
ex. quartz, ice
2
Q
mineraloids
A
- Similar to a mineral but no ordered arrangement of atoms
- Because of the lack of ordered atoms, is amorphous rather than crystalline
- Ex. Opal
3
Q
rocks
A
Aggregates of minerals (ex. Granite – made up of quartz, feldspars and biotite mica)
4
Q
atomic structures
A
- Protons, electrons, neutrons -> atoms -> elements -> minerals
- Element: form of matter that can’t be broken down into a simpler form
- Atom: smallest subdivision of matter that retains chemical properties of an element
5
Q
bonds
A
- attachments between atoms in a crystalline structure.
- Important because different bonds lead to different physical properties which can be used to identify minerals
- types of bonds: covalent, ionic, metallic, van der waals
6
Q
covalent, ionic, metallic, and van der waal bonds
A
- Covalent: ions shared, makes strong bonds (ie. Diamond)
- Ionic: ions given away
- Metallic: Weak covalent bond occuring in metallic elements, outer electons travel freely between adjacent atoms
- Van der Waals: weak bonds between slightly polarized atoms
7
Q
ions
A
- Atom that has positive or negative net charge due to gain or loss of electrons
- Cation = +, anion = -
8
Q
mineral groups
A
- Minerals divide into groups with like physical properties, based on their anionic groups (negatively charged part of mineral)
- Silicates
- Carbonates (important for limestone; ex. calcite, dolomite)
- Ore minerals (ex. galena, pyrite)
- Sulfates
- Sulfides
- Oxides
9
Q
silicates
A
- One third of all minerals -> 90-95% of earth’s crust
- Silica tetrahedron is basic building block of all silicate minerals
- Different arrangements of tetrahedrons lead to different minerals (ex. Isolate tetrahedron = olivine, single chain = pyroxene, double chain = amphibole, sheet structure = micas and clays, 3d framework = quartz and feldspar)
- Dark silicates (ferromagnesian) and light silicates (felsic)
10
Q
dark vs. light silicates
A
- Dark silicates = ferromagnesian
- High Mg, Fe content
- In oceanic crust
- Ex. Pyroxene, amphibole
- Light silicates = felsic
- Lack Fe
- Ex. Quartz, feldspar
11
Q
mineral composition of earth’s layers
A
- Crust
- Dominated by oxygen and silicates (94%)
- Minerals: fedspar, quartz - Mantle
- Heavier, denser
- Oxygen, silica, iron, and magnesium
- Minerals: Olivines, pyroxine - Core
- Probably composed of nickel and iron
- No direct samples (educated guess from geophysical evidence)
12
Q
identifying minerals using physical properties
A
- Each one has unique set of physical properties, such as:
- Hardness
- Cleavage
- Fracture
- Crystal form
- Streak and lustre
- Colour
- Taste
- Specific gravity
- Magnetism
- Reaction with acid
13
Q
hardness
A
- what scratches what?
- Mohs’ hardness scale
- 1 = weakest, 10 = strongest
- Weaker minerals can be scratched by stronger minerals
14
Q
cleavage
A
- ability for mineral to split along planes of weakness
- Quality: how smooth the faces are – perfect, imperfect, distinct, good, fair, poor
- Difficulty: how easily the cleavage breaks – easy, hard, difficult
- Weak bonds between layers and strong bonds within layers make it easy to splot (ie. Mica – perfect cleavage)
- With 2 or more cleavages, the angle between them can also help identify (ie. Feldspar is 90 degrees, amphibole isn’t)
15
Q
fracture
A
- tendency to break along an irregular surface not controlled by cleavage
- ex. Conchoidal fracture (curved, spiral/conch-shell-like fracture)
- Quartz often displays this
16
Q
crystal form
A
- result of atomic structure of atoms and bonding (different than cleavage)
- Ex. Quartz = hexagonal crystals, pyrite = cubic crystals
17
Q
streak and lustre
A
- Streak = colour of powder produced when mineral is scratched
- Lustre = way light interacts with the surface of a crystal (ex. Glassy, metallic)
18
Q
quartz
A
- Silicon dixoxide
- Hardness: 7
- Colour: colourless to variable
- Streak: colourless/white
- Cleavage: none
- Lustre: vitreous (glassy)
- May form hexogonal crystals and exhibit conchoidal fracture
19
Q
calcite
A
- Calcium carbonate
- Hardness: 3
- Colour: colourless to variable
- Streak: white
- Cleavage: 3 (very good, fractures into rhombs)
- Lustre: viretous (glassy)
- Reacts with hydrochloric acid, demonstrates double-refraction
20
Q
feldspar
A
- Potassium/sodium-calcium/aluminum silicate
- Hardness: 6
- Colour: variable
- Streak: white
- Cleavage: 1 very good and 1 good, meet close to 90 degrees
- Lustre: vitreous (glassy) to dull
21
Q
biotite mica
A
- Potassium iron aluminum silicate hydroxide
- Hardness: 2.5-3
- Colour: brown
- Streak: white
- Cleavage: 1 single very good cleavage (thin sheets)
- Lustre: vitreous (glassy) to pearly
- Thin, flexible cleavage sheets are very diagnostic
22
Q
pyrite
A
- Iron sulfide
- Hardness: 6-6.4
- Colour: brassy yellow
- Streak: black
- Cleavage: none
- Lustre: metallic
- May grown in the form of perfect cubes, feels heavy (high specific gravity)
23
Q
earth’s mineral evolution
A
- currently 4400 mineral species on earth (much higher than moon, Mercury, Mars)
- Early solar system started out with very little mineral diversity, until material in solar nebula clumped -> high temperature and pressure of planet formation cooked new minerals
- on some planets, volcanic activity and water cooked even more minerals (Mercury and Venus got here - 500 minerals)
- likely due to plate tectonics, earth went one step further -> new chemical and physical environments -> development of life (biggest influence) -> photosynthesis (mineral oxides can form) -> weathering and spread of plants (increase in clay minerals)
- Over half of today’s minerals are oxidized/hydrated -> can only happen on a planet rich in free oxygen
24
Q
how might minerals indicate whether there’s life on other planets?
A
- Clay minerals need liquid water to form
- Mineral oxides may indicate photsynthesis
25
Q
3 types of rocks
A
- Igneous: derived from melts (magma or lava)
- Sedimentary: from weathering or precipitation
- Metamorphic: from pre-existing rocks changed by higher pressure and temperature
26
Q
rock cycle
A
- rocks aren’t fixed, they can change over time
- No particular order to the stages – they’re interconnected
- Ex. Igneous rocks can be eroded into sedimentary or heated up and pressurized into a metamorphic, then get heated up so much they turn back into igneous
