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EOSC 118 MODULE B PRECIOUS GEMSTONES EXAM 2025 WITH 100% ACCURATE SOLUTIONS
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EOSC 118 MODULE B PRECIOUS GEMSTONES EXAM 2025 WITH 100% ACCURATE SOLUTIONS
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EOSC 118 MODULE B PRECIOUS GEMSTONES EXAM 2025 WITH 100%ACCURATE SOLUTIONS
8: Diamond - Answer
Summarize the historical sources of diamond prior to 1867 - Answer- First
appreciation in ancient India (octahedrons; euhedral shape)
- 1st century BC --> mentions of diamonds in Mediterranean; mentions of
diamond tools in Chinese literature
- Euro history of diamonds as far back as 13th century (royal jewelry)
- 17th century -> non-royal adornments of diamond
- historically extremely rare
- sourced only from a few alluvial (within river gravels) localities
- first discovered in Golconda Region of India --> then in Brazil by 18th
cent
Discuss the significance of the discovery of diamonds in South Africa in
1867 - Answer- discovery of diamond-bearing KIMBERLITE at Kimberley, S.
Africa in 1867 --> diamonds much more common, no longer royalty only
- middle class originally could have diamonds, then De Beers changed this
Summarize how the dominance of the De Beers group has changed in the
last century - Answer- Mined majority of diamonds and controlled flow to
consumers --> control over production and sale
- Kimberley Process
- rise of competitors changed the way diamonds polished, mined, sold -->
ethical
,What kind of deposits hosted the majority of historical diamonds from
Brazil and the Golconda region of India? - Answeralluvial localities and
sources
What happened in 1867 that made diamonds much more readily
accessible to consumers? - AnswerThe discovery of diamond-bearing
Kimberlite at Kimberley, S. Africa and its exploitation- diamonds more
accessible to upper and middle class
What is the Kimberley Process? - Answera non-government organization
that monitors the import/export diamond activity of participating
countries, ensuring that traded diamonds are legitimately conflict-free
9: Diamond Mineralogy and Gemology - Answer
Use the diagnostic properties of diamond (such as thermal conductivity,
composition, crystal structure, primary morphology, etc.) to identify it. -
Answer-10 on hardness scale
-high durability
-high refractive index of 2.42 !
-great dispersion of light !
-colourless
-HIGH THERMAL CONDUCTIVITY ! (due to covalent bonding that holds
carbon atoms together)
-low electrical conductivity !
Describe the cleavage of diamond and its importance for diamond cutters
- Answerperfect octahedral cleavage, cubic symmetry and dense
crystalline structure (3.51 g/cm3)
Diamond cutters require a good understanding of the mineral's
crystallography and where its inherent weaknesses lie in order to expertly
cut stones and grind the flat parts (facets) on a polished stone
,Differentiate between Type Ia, Ib, IIa, IIb diamonds in terms of composition
and colour - Answeramount of nitrogen that substituted into crystal
structure
Type I (N concentrations greater than 10 ppm)
Type Ia: N atoms occur in aggregates within the diamond (absorb blue,
show yellow) (most common)
Type Ib: N in diamond structure is dispersed (rare, appreciable N,
scattered about crystal lattice)
In the next level, Type Ia diamonds with clustered N are subdivided into
Types IaA with paired N atoms and IaB where 4 N atoms (quads) are
clustered often with a vacancy (void/absence of atoms) at their center.
Type II (N less than 10 ppm aka nitrogen-free)
Type IIa: boron (B) free (2nd most common, no N or B, whitest colour w/
little-no absorption of light)
Type IIb: contain up to 10 ppm of boron (some B, no N, absorb most light
except blue, shows blue to grey hue) (hope diamond?)
**MOST DIAMONDS IN TYPE IA GROUP (absorb blue, show yellow)
Identify the cause(s) of different colours of diamond - Answerpurity, boron
impurities, nitrogen impurities, deformation of crystal structure, natural
irradiation, abundant graphite and other opaque inclusions (green and red
diamonds most rare)
Identify common diamond treatments and methods of creating synthetic
diamonds - Answercommon diamond treatments altering techniques
-HPHT annealing (high pressure, high temp)(most common) (prevents
graphitization, alter states of nitrogen impurities and types, and heal
, lattice vacancies) --> removes the brown body colour to produce colours
or enhance yellow colour
-LPHT annealing (low pressure, high temp)(produces black appearance to
hide imperfections)
-irradiation
-glass-filling, laser-drilling, acid-boiling
methods of creating synthetic diamonds
1) Carbon Vapor Deposition (CVD)
2) High Pressure High Temperature Growth (HPHT)
Which of the following are common crystal habits of rough diamond?
-octahedral
-cubic
-prismatic
-dodecahedral - Answeroctahedron (most common)
cubic too
a) Which of these properties might a geologist use to identify a rough
diamond in the field?
b) Which of the properties might a gemologist used to distinguish a cut
diamond from some of its imitators, like cubic zirconia, glass, moissanite?
- Answera) thermal conductivity
b) electrical conductivity and refractive index, dispersion
Diamond has ________ thermal conductivity. - AnswerHIGH
What describes a Type IIa diamond? - Answerno nitrogen, no boron
Which type of diamond is the most common? - Answerdiamond type Ia
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