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Geology, LEC 172 > Minerals, Lectures 4 & 5 > Flashcards

Minerals, Lectures 4 & 5 Flashcards

1
Q

Minerals

A

Naturally occurring, inorganic crystalline solids.

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2
Q

Are minerals elements, atoms or compounds

A

elements or compounds

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3
Q

Crystalline

A

regular internal structure

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4
Q

Rocks make up…

A

rocks,

they are the building blocks of rocks

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5
Q

Rocks

A

naturally occurring solid aggregates of minerals

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6
Q

Main rock forming minerals

A

silicates

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7
Q

What do sillicates contain?

A

Si and O, combined with metallic elements

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8
Q

Example of a silicate mineral?

A

quartz

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9
Q

Two most abundant elements in the Earth’s crusts

A

silicon and oxygen

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10
Q

How do minerals form?

A

by crystallisation

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11
Q

Non-silicate minerals

6

A
  1. magnetite
  2. haematite
  3. pyrite
  4. gypsum
  5. calcite
  6. halite
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12
Q

Building block of silicate minerals

A

silica tetrahedron - SiO4

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13
Q

Third most abundant element in the Earth’s crust

A

Aluminium

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14
Q

How do silica tetrahedron made up minerals?

A

arranged in various ways with cations in the interstices

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15
Q

Four constituent minerals of granite

A

quartz
biotite (mica)
plagioclase feldspar
orthoclase feldspar

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16
Q

Crystal faces

A

The natural, flat (planar) boundaries of crystals.

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17
Q

If plenty of space how do crystal faces form?

A

slowly

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18
Q

If space is limited, how do crystals grow?

A

grow over and coalesce to become a solid mass of crystalline particles/grains - results in few or no grains showing crystal faces

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19
Q

Mineral solid solutions

A

Cations of similar sizes substitute for each other and make mixed compounds.

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20
Q

Example of a solid solutions

21
Q

Solid solution: olivine, what is it made up of?

22
Q

Pure Fe olivine

A

pure Fe olivine: Fe2SiO4

Fayalite

23
Q

Pure Mg olivine?

A

pure Mg olivine: Mg2SiO4

Forsterite

24
Q

Natural olivines are …

A

intermediate between foresterite and fayalite

25
What do all major silicate groups (except quartz) show?
some degree of solid solution
26
Natural glass
obsidian, volcanic glass
27
How does natural glass form?
Forms when lava cools too quickly to form crystals.
28
Structure of natural glass
Atoms are arranged in silica tetrahedra but, instead of being linked in a regular manner, they are randomly arranged as they would be in a liquid.
29
What are the layers in obsedian?
gas bubbles
30
Characteristics of obsedian colour 3
jet-black glassy (vitreous) lustre shiney
31
``` Characteristics of obsedian shape crystals? rock or mineral or neither? 4 ```
conchoidal (smoothly curved) fracture lack, or have very small crystals may have vesicles (bubbles) and flow bands not a rock or mineral
32
Polymorphism
When chemical substances form more than one kind of crystal structure: different structures are called polymorphs
33
Example of polymorphism CaCO3 which conditions for one of the polymorphs?
calcite and aragonite (higher density, stable at higher pressures)
34
What can calcite and aragonite make up?
shelly, invertebrate organisms such as foraminifera, clams and corals
35
Example of polymorphism carbon naturally occurring polymorphs
graphite and diamond
36
Example of polymorphism carbon not naturally occurring
fullerenes and graphene
37
Which naturally occurring carbon polymorph is more stable at higher pressures and has a higher density?
diamond
38
A mineral has...
a narrowly defined chemical composition and characteristics physical properties
39
Example of a characteristics physical property of a mineral?
hardness
40
Microscopy
the study of samples under the microscope
41
Petrography
the detailed description of rocks
42
What is used to see small minerals within rocks?
a polarising (petrographic) microscope and thin section (rock slices 0.03mm thick)
43
How are the minerals in rocks viewed under a polarising/petrographic microscope?
- rocks and mienrals become transparent if sliced thinly | - the microscope passes polarised light through
44
Polarised light
light vibrating in only one plane
45
Polariser
optical filter converts beam of light of mixed polarisation into beam with well defined polarisation
46
Two main ways of examining thin sections under a microscope
PPL and XPL
47
XPL
cross polarised light
48
PPL
plane polarised light
49
Pleochroism
An optical phenomenon in which a mineral appears to be a different colour when observed at different angles. different angle = different colour

Geology, LEC 172 (6 decks)

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