1.1 Minerals Flashcards

1
Q

What are minerals?

A

Substances with a definite chemical composition and atomic structure and formed by the inorganic processes of nature

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2
Q

What are minerals composed of?

A

Elements

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3
Q

What are the eight most common elements found in minerals?

A
  • oxygen
  • aluminium
  • calcium
  • potassium
  • silicon
  • iron
  • sodium
  • magnesium
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4
Q

What is the name of the mineral made from pure silica?

A

Quartz

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5
Q

What is the symbol for pure silica/quartz?

A

SiO2

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6
Q

What are the physical properties of minerals that are studied?

A
  • colour
  • streak
  • lustre
  • form or habit
  • cleavage
  • fracture
  • hardness
  • relative density
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7
Q

What are the chemical properties of minerals that are studied?

A
  • acid test

* taste test

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8
Q

What does the colour of a mineral depend on?

A

The colours of the spectrum that it reflects

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9
Q

What does it mean, in terms of reflection of light, if a mineral is colourless?

A

It allows most light to pass through it

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10
Q

What is the name of a colourless quartz?

A

Rock crystal

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11
Q

What is the name of a purple quartz?

A

Amythyst

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12
Q

What is the name of a yellow quartz?

A

Citrine

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13
Q

What is the name of a brown quartz?

A

Smoky quartz

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14
Q

What is the name of a pink quartz?

A

Rose quartz

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15
Q

What is the name of a white quartz?

A

Milky quartz

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16
Q

What is the streak of a mineral?

A

The colour of a mineral’s powder

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17
Q

How is the streak of a mineral seen?

A

By rubbing it on a piece of unglazed porcelain (streak plate)

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18
Q

Is the colour of a mineral’s streak necessarily the same as its normal colour?

A

No

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19
Q

What colour streak does black haematite have?

A

Red

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20
Q

What happens if minerals are harder than the streak plate?

A

They will have no streak

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21
Q

What is the lustre of a mineral?

A

The amount and quality of light that it reflects

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22
Q

What terms can be used to describe lustre?

A
  • metallic
  • vitreous (glassy)
  • adamantine
  • dull
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23
Q

What is a metallic lustre?

A

The ordinary lustre of metals

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24
Q

What is a vitreous lustre?

A

The lustre of broken glass

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25
Q

What is an adamantine lustre?

A

The brilliant lustre of diamond

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26
Q

What is a dull lustre?

A

Having little or no lustre

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27
Q

What is the form or habit of a mineral?

A

The common shape a mineral takes

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28
Q

What terms are used to describe crystal structure?

A
  • crystallised
  • crystalline
  • cryptocrystalline
  • amorphous
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29
Q

What does it mean if a mineral is crystallised?

A

The mineral occurs as well developed crystals

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30
Q

What does it mean if a mineral is crystalline?

A

A confused mixture of imperfect crystals

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31
Q

What does it mean if a mineral is cryptocrystalline?

A

Mere traces of crystalline structure

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32
Q

What does it mean if a mineral is amorphous?

A

No crystalline structure - this is quite rare

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33
Q

What is the crystal structure of peridot?

A

Crystallised

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34
Q

What is the crystal structure of fluorite?

A

Crystalline

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35
Q

What is the crystal structure of gypsum?

A

Cryptocrystalline

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36
Q

What is the crystal structure of graphite?

A

Amorphous

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37
Q

What are other common shapes among minerals (not crystalline, crystallised etc.)?

A
  • cubic
  • rhombic
  • hexagonal
  • reniform (kidney shaped)
  • nodular
  • columnar
  • fibrous
  • foliated
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38
Q

What does it mean if a mineral is nodular?

A

Detached, rounded masses

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39
Q

What does it mean if a mineral is foliated?

A

Thin layers or lamellae

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40
Q

What is the cleavage of a mineral?

A

The tendency to split along definite planes, known as cleavage planes

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41
Q

What direction are cleavage planes in?

A

Parallel to crystal forms

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42
Q

How is cleavage described?

A

Good/poor

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43
Q

Types of cleavage?

A
  • cubic cleavage - 3 directions
  • rhombohedral - 3 directions
  • basal cleavage - 1 direction
44
Q

What is fracture?

A

The irregular way in which a mineral breaks apart

45
Q

What are the 3 main types of fracture?

A
  • uneven - rough surface
  • hackly
  • conchoidal
46
Q

What is hackly fracture?

A

A surface studded with sharp and jagged elevations

47
Q

What is conchoidal fracture?

A

Concave or convex surface with concentric lines (like a shell)

48
Q

What scale is used to test hardness?

A

Moh’s scale

49
Q

What does it mean if you can scratch a mineral with your fingernail?

A

It has hardness of less than 2.5

50
Q

What does it mean if you can scratch a mineral with a copper coin?

A

It has a hardness between 3.5 and 2.5

51
Q

What does it mean if you can scratch a mineral with a steel pin?

A

It has a hardness between 3.5 and 5.5

52
Q

What does it mean if you can’t scratch a mineral with a steel pin?

A

It has hardness more than 5.5

53
Q

What is the relative density of a mineral?

A

Shows the number of times heavier that mineral is than an equal volume of water

54
Q

How to calculate relative density?

A

Mass of specimen in air (g) / water displaced by specimen (cm3)

55
Q

What is the commonly used test for calcite?

A

Acid test

56
Q

What is the most important mineral in limestone?

A

Calcite

57
Q

How is an acid test carried out?

A

Dilute HCl dropped on the mineral, which bubbles and gives of CO2

58
Q

What is the taste test used to identify?

A

Halite

59
Q

Why is halite salty?

A

Composed of NaCl

60
Q

How can minerals be formed?

A
  • crystallisation from a melt
  • metamorphic crystallisation
  • crystallisation from solution in evaporating water
  • crystallisation as a cement from flowing pore waters
  • crystallisation from hydrothermal fluids
61
Q

What type of rocks does crystallisation from a melt generally apply to?

A

Igneous rocks

62
Q

How does crystallisation from a melt form minerals?

A

Minerals crystallise when magma cools to form igneous rocks

63
Q

What happens when magma cools very rapidly?

A

Volcanic glass is formed

64
Q

When will big crystals form?

A

When magma deep in the crust cools slowly

65
Q

When will small crystals form?

A

When magma that pours out onto the surface of the crust cools rapidly

66
Q

When will both big and small crystals form?

A

When magma cooling partly deep in the crust and partly on the surface

67
Q

What minerals does granite contain?

A
  • mica
  • quartz
  • feldspar
68
Q

When does metamorphism occur?

A

When rocks are changed by an increase in temperature and/or pressure

69
Q

Does metamorphism involve a liquid phase?

A

No - it is a change from one solid to another

70
Q

Which minerals are formed by crystallisation from a melt?

A
  • quartz
  • mica
  • feldspar
  • olivine
  • augite
71
Q

Which minerals are formed by metamorphic recrystallisation?

A
  • calcite

* garnet

72
Q

Which minerals are formed by crystallisation from solution in evaporating water?

A

Halite

73
Q

Which minerals are formed by crystallisation as cement from flowing pore waters?

A
  • quartz

* calcite

74
Q

Which minerals are formed by crystallisation from hydrothermal fluids?

A

gangue minerals:

  • quartz
  • calcite

ore minerals:

  • haematite
  • galena
75
Q

In metamorphic recrystallisation, what does higher temperatures mean for crystal size?

A

Larger crystals

76
Q

In metamorphic recrystallisation, what do higher pressures mean for crystal size?

A

Produce layering in the rock - foliation

77
Q

What is evaporite?

A

Substances left behind from evaporation

78
Q

When does a solution become saturated?

A

When it is heated by the sun

79
Q

How is halite formed?

A
  • minerals carried into lake in solution
  • sun heats up lake waters
  • evaporation of lake waters
  • halite precipitated out from solution
80
Q

How are minerals formed by crystallisation as a cement from flowing pore waters?

A
  • when sediment deposited it will only become hard sedimentary rock if it is cemented by minerals
  • water in pores between sediments carries dissolved minerals which are precipitated out between clasts
  • minerals bind clasts together form the cement of the rock
81
Q

What are the three main minerals that form cements in sedimentary rocks?

A
  • stiperstones conglomerate - quartz
  • wenlock limestone - calcite
  • navajo sandstone - haematite
82
Q

What is haematite also known as?

A

Iron oxide

83
Q

Where are hydrothermal minerals deposited from?

A

Hot water solutions

84
Q

How do hydrothermal minerals form?

A

From the heated waters given off by magma as it cools - these hot waters can dissolve and carry metals

85
Q

What are the deposits of metallic minerals called?

A

Ores

86
Q

When hot water solutions are cooled, how can the elements crystallise?

A
  • in cavities or fissures as hydrothermal veins

* in between the grains of sediments as impregnations

87
Q

What are gangue minerals?

A

The minerals in hydrothermal veins that are not ores and not of any value e.g. quartz and calcite

88
Q

What happens when some minerals form at higher temperatures in hydrothermal veins?

A

This causes the vein to show the minerals as zones

89
Q

How are minerals in sedimentary rocks most often found?

A

As clasts (grains)

90
Q

Which characteristics of clasts in sedimentary rocks can determine how much transportation and erosion has taken place?

A
  • size - given by the length of its long axis
  • sorting - how close clasts are to being the same size
  • roundness
  • sphericity
91
Q

What are the three main methods of prospecting for minerals?

A
  • field mapping
  • geophysical techniques
  • geochemical techniques
92
Q

What is field mapping?

A

Involves analysing geology of an area in a field, producing a field map and therefore suggested locations for mineral exploitation

93
Q

What are the geophysical techniques of prospecting?

A
  • magnetic surveys
  • seismic surveys
  • electrical surveys
94
Q

What are magnetic surveys?

A

Using a magnetometer, ore bodies are picked out as they show a stronger magnetism as they are more able to take on the earth’s magnetic field

95
Q

What are seismic surveys?

A

Using seisometers, they discover mineral reserves but are more widely used in the petroleum industry

96
Q

What are electric surveys?

A

Ore bodies conduct an electric current more easily than other geological materials - a resistivity survey involves passing current through the crust to show location of ore body

97
Q

What are the geochemical techniques of prospecting?

A
  • soil and sediment sampling

* water sampling

98
Q

How can soil and sediment sampling prospect minerals?

A

Soil and sediment are formed from breakdown of rock, so may contain evidence of ore bodies that lie beneath the surface

99
Q

How can water sampling prospect minerals?

A

Water may contain small amounts of metallic elements that indicate water has passed over an ore body

100
Q

What are the problems with prospecting using water sampling?

A

Water can be contaminated because concentrations of metals are low, and variations in acidity make interpretation difficult

101
Q

What are the methods used to mine minerals?

A
  • mining hydrothermal veins
  • mining large ore bodies
  • mining evaporite deposits
102
Q

How are hydrothermal veins mined?

A

Using the adit and stope method

103
Q

What is the adit and stope method of mining?

A
  • adit - tunnel driven into hillside at a low angle to get to vein
  • stope - tunnel dug along line of veins
  • stope and adits join to create complex of tunnels in the mine
104
Q

How can ore minerals be extracted when found in large bodies?

A

By the process of open cast mining - only for when ore is near the surface. Remove overlying rock.

105
Q

How can halite be mined from evaporite?

A

When found near surface, use pillar and stall method

106
Q

What is the pillar and stall method of mining in evaporite deposits?

A

Removing most of halite but leaving pillars so support roof of mine`

107
Q

Why is halite good for the pillar and stall method of mining?

A

It does not fracture, behaves in a plastic manner