CMU Questions Flashcards
From which country do the majority of the 10 largest diamonds ever found originate?
South Africa
(Lesson 2)
What makes some gemstones “priceless”?
Historical and cultural significance
(2)
Which is a top producing country for both diamonds and platinum group metals?
South Africa
(3)
What is the main use of platinum group metals?
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)
What is the gold standard?
An international standard for which national currenciees can be valued against
(4)
By purchasing a Maple Leaf diamond, you can be sure that the diamond you have purchased…
was mined in Canada
(4)
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
mineral
(5)
A ____ is a naturally occuring aggregate of minerals.
rock
(5)
Can a rock be a gemstone?
yes
(5)
Are all gemstones minerals?
no
(5)
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
b. iron ore within hematite
(6)
Which of the following is the unit most commonly used to define the weight of gemstones?
a. carat
b. karat
c. gram
a. carat
(6)
If you had a ring that was 75% pure gold, it would have a purity of ___ karats (Kt).
18
Pure = 24 Kt
18/24 = 3/4 = 75%
(6)
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 metal
(Quiz 1)
T/F
Covalent and metallic bonding both involve sharing of valence electrons
True
Covalent bonding: sharing of valence electrons
Metallic bonding: sharing of valence electrons throughout the entire material
(Quiz 1)
T/F
Ionic bonding occurs when positively-charged ions donate electrons to negatively-charged cations
False
Ionic bonding: positively-charged cations donate electrons to negatively-charged anions
(Quiz 1)
T/F
Metallic bonding is the weakest type of bond compared to covalent and ionic bonding
True
(Quiz 1)
T/F
Diamond (C) contains covalent bonds
True
This accounts for diamond’s high hardness
(Quiz 1)
You want to buy 100 ounces of a metal, but you buy 100 troy ounces by mistake. What is the difference?
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)
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?
Metamorphic rock
(Quiz 1)
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-)
2
Before considering the sodium:
(2- * 3) + (4+ * 1) = 2-
Each sodium is 1+, so we need 2 to balance the charge
(Quiz 1)
Which elements are primarily used for applications that require good chemical durability, such as in the creation of autocatalysts and electronics?
PGMs
Cu
(Quiz 1)
The atomic mass of an atom refers to the number of ___.
protons and neutrons
(Quiz 1)
What factors are required for element substitution?
same valence charge
similar ionic radius
(Quiz 1)
How do volcanic rocks form?
These igneous rocks form from cooling on the surface of the Earth
(Quiz 1)
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
density, fluorescence, and dispersion
(hardness and streak will damage the sample)
(Quiz 1)
What are gemstones?
Any materials highly valued for their beauty, durability, and/or rarity.
They can be inorganic or organic in origin, but are typically minerals.
What are metamorphic rocks?
Rocks altered from their original state by heat and/or pressure (and sometimes hydrothermal fluids).
T/F
All gemstones are minerals
False
(Quiz 1)
T/F
All minerals are crystalline
True
(Quiz 1)
T/F
Not all minerals are gemstones
True
(Quiz 1)
T/F
Some rocks can be gemstones
True
(Quiz 1)
What kind of gemstone is the ‘Dresden Green’, and why is it green hued?
Diamond; exposure to radiation
Name the four main native minerals.
Which properties do they have in common?
Gold (Au), silver (Ag), Copper (Cu), and platinum (Pt).
- good electrical conductivity
- good thermal conductivity
- metallic luster
(Quiz 1)
Why is plate tectonics known as the geological grand unifying theory?
- 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)
Diamond has ___ thermal conductivity
very high
(9)
What describes a Type IIa diamond?
Type IIa diamonds contain no nitrogen or boron impurities
(9)
What type of diamond is the most common?
Type Ia
(9)
What is the most common habit for diamonds?
Octahedral
(9)
Do all kimberlites contain diamonds?
no
(10)
Why does the speed of kimberlite ascent increase as it gets closer to the surface?
There is less overlying pressure closer to the surface
(10)
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
country of origin (not required, but could be included)
(11)
Ten carats are equivalent to __ grams.
2
One carat = 0.2 grams
(11)
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?
Anisotropic (anisotropic minerals have more than one refractive index)
(13)
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.
translucent
jade
(13)
The beryl crystal structure requires which rare element?
Beryllium (Be)
(14)
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)
chromium and vanadium
(14)
V3+ (vanadium) substitutions for Al3+ (aluminum) result in which gemstone variety of beryl?
Emerald
(15)
Mn3+ (manganese) substitutions for Al3+ (aluminum) result in which gemstone variety of beryl?
Morganite (pink beryl)
manganese produces the pink colour
(15)
What elements produce the colouring for:
- aquamarine and heliodor
- emerald
- goshenite
aquamarine and heliodor: Fe
emerald: Cr and/or V
goshenite: lack of colour due to lack of impurities
(15)
What is a common treatment for emeralds?
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)
T/F
Beryl is harder than quartz
True
(15)
Where did the beryllium (Be) that formed the famous Columbian emeralds come from?
Hydrothermal fluids rich in Be reacted with Cr-rich host rocks
(16)
Why is aquamarine relatively rare?
It requires beryllium to form
- there is very little Be in the Earth’s crust
- only certain rock types will concentrate Be
(16)
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
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)
Name the “Big Three” coloured gemstones and their parent minerals.
Emerald (beryl), ruby & sapphire (corundum)
(17)
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
Magnesium
(Quiz 2)
Why has De Beers dominance in the diamond market lessened in recent decades?
Other companies have entered the market, introducing competition
What is HPHT?
High pressure high temperature annealing
A diamond treatment known for removing brown colour
(Quiz 2)
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?
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)
Where are kimberlite volcanoes, and therefore diamonds, most likely to be found?
within an Archean craton, >2.5 billion years old
(Quiz 2)
What factors contribute to diamond’s rareness?
- 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)
T/F
Diamond can be formed in an environment 150km below the surface where the temperature is 1500 degrees C
False
The temperature is too high to form diamonds
(Quiz 2)
Suppose the light energy of a particular wave decreases. What can we assume about the wave?
the frequency of the wave decreases
the wavelength of the wave increases
(Quiz 2)
Choose all the elements corundum is composed of
- aluminum
- oxygen
- beryllium
- carbon
- silicon
Al2O3
aluminum and oxygen
(18)
What colour is pure corundum?
colourless
(18)
Name a stone that has historically often been mistaken for ruby
Spinel
- almost as hard
- can show bright red colouration
One example of a notable locality for xenocrystic gem corundum is ___.
Southeast Asia
(19)
One example of a notable locality for marble-hosted gem ocorundum is ___.
Myanmar
(19)
What is a common feature of Madagascar, Myanmar, and Sri Lanka that makes them favourable for secondary accumulations of gem corundum?
High rates of tropical weathering which concentrates heavy minerals in placer deposits
(19)
What is similar about the geological setting in which diamonds and xenocrystic corundum are formed?
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)
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)
rare-element pegmatite types are most productive
–> miarolitic can also contain significant gemstones
(20)
Which of the following is not known for its gem-bearing pegmatites?
a. Chile
b. Pakistan
c. USA
d. Italy
a. Chile
(20)
High volatile concentration is critical for pegmatite formation, but what happens when volatile concentration is too high at the end of pegmatite formation?
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)
What feature is not useful in identifying tourmaline in hand sample?
Cleavage - tourmaline has very poor cleavage
Useful:
pseudo-hexagonal habit
vertical striations along c-axis of crystal
dichroism
hardness (7-7.5)
(21)
Which are gem varieties of spodumene?
a. kunzite
b. hiddenite
c. heliodor
d. morganite
e. elbaite
a (pink) & b (green)
morganite: pink beryl
heliodor: yellow gem beryl
elbaite: pink tourmaline
(21)
What type of metal deposit is turquoise typically associated with?
Copper
(22)
Pearl is:
a. a gemstone
b. organic
c. a rock
d. a mineral
e. inorganic
a & b
(22)
What
