Minerals

Question 1

5 requirements of a mineral

Answer 1

• Solid
• Naturally occurring
• Fixed chemical composition
• Crystalline structure
• Inorganic
  ex. quartz, ice

Question 2

mineraloids

Answer 2

• Similar to a mineral but no ordered arrangement of atoms
• Because of the lack of ordered atoms, is amorphous rather than crystalline
• Ex. Opal

Question 3

rocks

Answer 3

Aggregates of minerals (ex. Granite – made up of quartz, feldspars and biotite mica)

Question 4

atomic structures

Answer 4

• 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

Question 5

bonds

Answer 5

• 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

Question 6

covalent, ionic, metallic, and van der waal bonds

Answer 6

• 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

Question 7

ions

Answer 7

• Atom that has positive or negative net charge due to gain or loss of electrons
• Cation = +, anion = -

Question 8

mineral groups

Answer 8

• 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

Question 9

silicates

Answer 9

• 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)

Question 10

dark vs. light silicates

Answer 10

• Dark silicates = ferromagnesian
• High Mg, Fe content
• In oceanic crust
• Ex. Pyroxene, amphibole
• Light silicates = felsic
• Lack Fe
• Ex. Quartz, feldspar

Question 11

mineral composition of earth’s layers

Answer 11

1. Crust
   - Dominated by oxygen and silicates (94%)
   - Minerals: fedspar, quartz
2. Mantle
   - Heavier, denser
   - Oxygen, silica, iron, and magnesium
   - Minerals: Olivines, pyroxine
3. Core
   - Probably composed of nickel and iron
   - No direct samples (educated guess from geophysical evidence)

Question 12

identifying minerals using physical properties

Answer 12

• 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

Question 13

hardness

Answer 13

• what scratches what?
• Mohs’ hardness scale
• 1 = weakest, 10 = strongest
• Weaker minerals can be scratched by stronger minerals

Question 14

cleavage

Answer 14

• 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)

Question 15

fracture

Answer 15

• tendency to break along an irregular surface not controlled by cleavage
• ex. Conchoidal fracture (curved, spiral/conch-shell-like fracture)
• Quartz often displays this

Question 16

crystal form

Answer 16

• result of atomic structure of atoms and bonding (different than cleavage)
• Ex. Quartz = hexagonal crystals, pyrite = cubic crystals

Question 17

streak and lustre

Answer 17

• Streak = colour of powder produced when mineral is scratched
• Lustre = way light interacts with the surface of a crystal (ex. Glassy, metallic)

Question 18

quartz

Answer 18

• Silicon dixoxide
• Hardness: 7
• Colour: colourless to variable
• Streak: colourless/white
• Cleavage: none
• Lustre: vitreous (glassy)
• May form hexogonal crystals and exhibit conchoidal fracture

Question 19

calcite

Answer 19

• 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

Question 20

feldspar

Answer 20

• 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

Question 21

biotite mica

Answer 21

• 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

Question 22

pyrite

Answer 22

• 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)

Question 23

earth’s mineral evolution

Answer 23

• 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

Question 24

how might minerals indicate whether there’s life on other planets?

Answer 24

• Clay minerals need liquid water to form

- Mineral oxides may indicate photsynthesis

Question 25

3 types of rocks

Answer 25

- Igneous: derived from melts (magma or lava) - Sedimentary: from weathering or precipitation - Metamorphic: from pre-existing rocks changed by higher pressure and temperature

Question 26

rock cycle

Answer 26

- 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