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Rocks, Minerals, and Gems > CMU Questions > Flashcards

CMU Questions Flashcards

1
Q

From which country do the majority of the 10 largest diamonds ever found originate?

A

South Africa

(Lesson 2)

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2
Q

What makes some gemstones “priceless”?

A

Historical and cultural significance

(2)

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3
Q

Which is a top producing country for both diamonds and platinum group metals?

A

South Africa

(3)

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4
Q

What is the main use of platinum group metals?

A

Autocatalysts
- used in a vehicle’s exhaust line to convert pollutants from the combustion of fuel into harmless gases (HC, CO, and NOx –> H2O, CO2, and N)
- consist of a cylinder/elliptical cross section made from ceramic or metal formed into a fine honeycomb; this is coated with a solution of chemicals and a combination of platinum, rhodium, and/or palladium

Other uses: jewellery and electronics

(3)

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5
Q

What is the gold standard?

A

An international standard for which national currenciees can be valued against

(4)

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6
Q

By purchasing a Maple Leaf diamond, you can be sure that the diamond you have purchased…

A

was mined in Canada

(4)

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7
Q

A ____ is a (i) naturally occuring, (ii) homogenous solid with a (iii) definite (but generally not fixed) chemical composition and a (iv) crystalline structure. It is usually formed by (v) inorganic processes

A

mineral

(5)

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8
Q

A ____ is a naturally occuring aggregate of minerals.

A

rock

(5)

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9
Q

Can a rock be a gemstone?

A

yes

(5)

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10
Q

Are all gemstones minerals?

A

no

(5)

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11
Q

Which of the following is not a native element/metal/mineral?
a. a pure gold nugget
b. iron ore within hematite (Fe2O3)
c. diamond
d. platinum

A

b. iron ore within hematite

(6)

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12
Q

Which of the following is the unit most commonly used to define the weight of gemstones?
a. carat
b. karat
c. gram

A

a. carat

(6)

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13
Q

If you had a ring that was 75% pure gold, it would have a purity of ___ karats (Kt).

A

18

Pure = 24 Kt
18/24 = 3/4 = 75%

(6)

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14
Q

An object is described as having a shiny appearance. It is also a good conductor of electricity and it bends easily. What is it?

A

A metal

(Quiz 1)

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15
Q

T/F
Covalent and metallic bonding both involve sharing of valence electrons

A

True

Covalent bonding: sharing of valence electrons
Metallic bonding: sharing of valence electrons throughout the entire material

(Quiz 1)

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16
Q

T/F
Ionic bonding occurs when positively-charged ions donate electrons to negatively-charged cations

A

False

Ionic bonding: positively-charged cations donate electrons to negatively-charged anions

(Quiz 1)

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17
Q

T/F
Metallic bonding is the weakest type of bond compared to covalent and ionic bonding

A

True

(Quiz 1)

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18
Q

T/F
Diamond (C) contains covalent bonds

A

True
This accounts for diamond’s high hardness

(Quiz 1)

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19
Q

You want to buy 100 ounces of a metal, but you buy 100 troy ounces by mistake. What is the difference?

A

100 troy ounces is 310 grams more than what you intended to buy.
1 troy ounce = ~31.1 grams
1 ounce = 28 grams

(Quiz 1)

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20
Q

If basalt, a type of igneous rock, were to undergo extensive changes in heat and pressure (without melting), what type of rock would it become?

A

Metamorphic rock

(Quiz 1)

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21
Q

For the compound NaxCO3 where x=the subscript for sodium, how many sodium atoms would it take to make this mineral neutrally charged?
(The charges of the atoms are provided as:
Na=1+, C=4+, O=2-)

A

2
Before considering the sodium:
(2- * 3) + (4+ * 1) = 2-
Each sodium is 1+, so we need 2 to balance the charge

(Quiz 1)

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22
Q

Which elements are primarily used for applications that require good chemical durability, such as in the creation of autocatalysts and electronics?

A

PGMs
Cu

(Quiz 1)

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23
Q

The atomic mass of an atom refers to the number of ___.

A

protons and neutrons

(Quiz 1)

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24
Q

What factors are required for element substitution?

A

same valence charge
similar ionic radius

(Quiz 1)

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25
Q

How do volcanic rocks form?

A

These igneous rocks form from cooling on the surface of the Earth

(Quiz 1)

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26
Q

If similar colour and luster are noted on two different mineral samples, which other physical properties could you test/observe without incurring damage to the sample in order to identify and differentiate them?
-density (specific gravity)
-fluorescence
-hardness
-streak
-dispersion

A

density, fluorescence, and dispersion
(hardness and streak will damage the sample)

(Quiz 1)

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27
Q

What are gemstones?

A

Any materials highly valued for their beauty, durability, and/or rarity.
They can be inorganic or organic in origin, but are typically minerals.

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28
Q

What are metamorphic rocks?

A

Rocks altered from their original state by heat and/or pressure (and sometimes hydrothermal fluids).

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29
Q

T/F
All gemstones are minerals

A

False

(Quiz 1)

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30
Q

T/F
All minerals are crystalline

A

True

(Quiz 1)

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31
Q

T/F
Not all minerals are gemstones

A

True

(Quiz 1)

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32
Q

T/F
Some rocks can be gemstones

A

True

(Quiz 1)

33
Q

What kind of gemstone is the ‘Dresden Green’, and why is it green hued?

A

Diamond; exposure to radiation

34
Q

Name the four main native minerals.
Which properties do they have in common?

A

Gold (Au), silver (Ag), Copper (Cu), and platinum (Pt).
- good electrical conductivity
- good thermal conductivity
- metallic luster

(Quiz 1)

35
Q

Why is plate tectonics known as the geological grand unifying theory?

A
  • it explains geological phenomena such as the processes that build mountains and the patterns of distribution of earthquakes and volcanoes
  • it describes how the plates and hence the continents pushed apart and pulled together the surface of the Earth
  • it allows generalized explanations of geologic features to be applied, regardless of a particular region

(Quiz 1)

36
Q

Diamond has ___ thermal conductivity

A

very high

(9)

37
Q

What describes a Type IIa diamond?

A

Type IIa diamonds contain no nitrogen or boron impurities

(9)

38
Q

What type of diamond is the most common?

A

Type Ia

(9)

39
Q

What is the most common habit for diamonds?

A

Octahedral

(9)

40
Q

Do all kimberlites contain diamonds?

A

no

(10)

41
Q

Why does the speed of kimberlite ascent increase as it gets closer to the surface?

A

There is less overlying pressure closer to the surface

(10)

42
Q

Which of the following is not generally included on a GIA diamond grading report?
- carat weight
- size (dimensions)
- diagram of inclusions within the stone
- country of origin

A

country of origin (not required, but could be included)

(11)

43
Q

Ten carats are equivalent to __ grams.

A

2
One carat = 0.2 grams

(11)

44
Q

The mineral dravite (a member of the tourmaline group) has refractive indices of nω = ~1.648 and nε = ~1.622. Is this mineral isotropic or anisotropic?

A

Anisotropic (anisotropic minerals have more than one refractive index)

(13)

45
Q

A ___ mineral is one where objects cannot be viewed through the medium, although light passes through but with lesser intensity. ___ is an example of this type of mineral.

A

translucent
jade

(13)

46
Q

The beryl crystal structure requires which rare element?

A

Beryllium (Be)

(14)

47
Q

For beryl to be considered emerald, many experts argue that it must contain which of the following elements?
- Chromium (Cr)
- Vanadiun (V)
- Iron (Fe)
- Manganese (Mn)

A

chromium and vanadium

(14)

48
Q

V3+ (vanadium) substitutions for Al3+ (aluminum) result in which gemstone variety of beryl?

A

Emerald

(15)

49
Q

Mn3+ (manganese) substitutions for Al3+ (aluminum) result in which gemstone variety of beryl?

A

Morganite (pink beryl)
manganese produces the pink colour

(15)

50
Q

What elements produce the colouring for:
- aquamarine and heliodor
- emerald
- goshenite

A

aquamarine and heliodor: Fe
emerald: Cr and/or V
goshenite: lack of colour due to lack of impurities

(15)

51
Q

What is a common treatment for emeralds?

A

Oiling: emeralds are often treated with basic cedar oils to fill fractures
- refractive index of the oil is matched to the refractive index of beryl (~1.44)
Some newer treatments use epoxies and other structural stabilizers

(15)

52
Q

T/F
Beryl is harder than quartz

A

True

(15)

53
Q

Where did the beryllium (Be) that formed the famous Columbian emeralds come from?

A

Hydrothermal fluids rich in Be reacted with Cr-rich host rocks

(16)

54
Q

Why is aquamarine relatively rare?

A

It requires beryllium to form
- there is very little Be in the Earth’s crust
- only certain rock types will concentrate Be

(16)

55
Q

In which geologic settings could it be possible to find emerald?
a. within the core of a pegmatite
b. in a secondary eluvial deposit
c. in Cr-bearing host rocks that border a pegmatite
d. in Fe- bearing host rocks that border a granitic intrusion

A

b & c

b: if Cr and/or V were present at the time of crystallization, emerald could be eroded and concentrated in an eluvial deposit

c: at their border, the fluid of Cr-bearing host rocks could mix with the fluid of the Be-bearing pegmatite to allow emerald to crystallize

Fe –> aquamarine
Cr and V aren’t appreciable in a pegmatite

(16)

56
Q

Name the “Big Three” coloured gemstones and their parent minerals.

A

Emerald (beryl), ruby & sapphire (corundum)

(17)

57
Q

Which element below would be most likely to substitute for zinc in the mineral sphalerite (ZnS)?

Element // Charge // Ionic radius
Zinc // 2+ // 0.74
Titanium // 4+ // 0.605
Magnesium // 2+ // 0.72
Lead // 2+ // 1.91
Sodium // 1+ // 1.02

A

Magnesium

(Quiz 2)

58
Q

Why has De Beers dominance in the diamond market lessened in recent decades?

A

Other companies have entered the market, introducing competition

59
Q

What is HPHT?

A

High pressure high temperature annealing
A diamond treatment known for removing brown colour

(Quiz 2)

60
Q

You are shown two diamonds with the following characteristics:

Diamond 1
- 8 sides
- 2 carats
- type IIa
- longest dimension = 8 mm

Diamond 2
- 12 sides
- 1.2 carats
- type Ia
- longest dimension = 6.2 mm

Do they have different crystal habits? Crystal systems? Values? Chemical compositions?

A

Different habits - 8 vs 12 sides –> diamond 2 has undergone secondary modifications to its crystal shape

Same cubic crystal system

Diamond 1 is likely more expensive (larger, no impurities)

Both are pure carbon; trace elements do not affect chemistry

(Quiz 2)

61
Q

Where are kimberlite volcanoes, and therefore diamonds, most likely to be found?

A

within an Archean craton, >2.5 billion years old

(Quiz 2)

62
Q

What factors contribute to diamond’s rareness?

A
  • the environment diamond is formed in is far below the surface of the Earth
  • unique geological conditions are required to transport diamonds to the Earth’s surface
  • the historical rareness of diamonds has influenced how we regard the rareness of diamonds today

(Quiz 2)

63
Q

T/F
Diamond can be formed in an environment 150km below the surface where the temperature is 1500 degrees C

A

False
The temperature is too high to form diamonds

(Quiz 2)

64
Q

Suppose the light energy of a particular wave decreases. What can we assume about the wave?

A

the frequency of the wave decreases
the wavelength of the wave increases

(Quiz 2)

65
Q

Choose all the elements corundum is composed of
- aluminum
- oxygen
- beryllium
- carbon
- silicon

A

Al2O3
aluminum and oxygen

(18)

66
Q

What colour is pure corundum?

A

colourless

(18)

67
Q

Name a stone that has historically often been mistaken for ruby

A

Spinel
- almost as hard
- can show bright red colouration

68
Q

One example of a notable locality for xenocrystic gem corundum is ___.

A

Southeast Asia

(19)

69
Q

One example of a notable locality for marble-hosted gem ocorundum is ___.

A

Myanmar

(19)

70
Q

What is a common feature of Madagascar, Myanmar, and Sri Lanka that makes them favourable for secondary accumulations of gem corundum?

A

High rates of tropical weathering which concentrates heavy minerals in placer deposits

(19)

71
Q

What is similar about the geological setting in which diamonds and xenocrystic corundum are formed?

A

Both are formed at great depths and brought to the surface by magma of a different composition
diamonds –> kimberlite volcanoes
xenocrystic corundum –> formed in rift zones where hot mantle plume breaks apart continental plate

(19)

72
Q

Which of these pegmatite classes is most likely to contain gemstones?
- abyssal (high temp, variable pressure)
- muscovite (low temp, high pressure)
- rare-element (low temp, low pressure)
- miarolitic (medium temp, low pressure)

A

rare-element pegmatite types are most productive
–> miarolitic can also contain significant gemstones

(20)

73
Q

Which of the following is not known for its gem-bearing pegmatites?
a. Chile
b. Pakistan
c. USA
d. Italy

A

a. Chile

(20)

74
Q

High volatile concentration is critical for pegmatite formation, but what happens when volatile concentration is too high at the end of pegmatite formation?

A

Corrosion of minerals
- volatiles allow diffusion of elements within the pegmatite melt and hydrothermal fluids, but extreme concentration can lead to corrosion of earlier formed minerals

(20)

75
Q

What feature is not useful in identifying tourmaline in hand sample?

A

Cleavage - tourmaline has very poor cleavage

Useful:
pseudo-hexagonal habit
vertical striations along c-axis of crystal
dichroism
hardness (7-7.5)

(21)

76
Q

Which are gem varieties of spodumene?
a. kunzite
b. hiddenite
c. heliodor
d. morganite
e. elbaite

A

a (pink) & b (green)

morganite: pink beryl
heliodor: yellow gem beryl
elbaite: pink tourmaline

(21)

77
Q

What type of metal deposit is turquoise typically associated with?

A

Copper

(22)

78
Q

Pearl is:
a. a gemstone
b. organic
c. a rock
d. a mineral
e. inorganic

A

a & b

(22)

79
Q

What

A

Rocks, Minerals, and Gems (18 decks)

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