EOSC 118 EXAM WITH COMPLETE
SOLUTIONS 100% CORRECT
Methods for synthetically producing diamonds - Answer- Carbon Vapour Deposition
(CVD), High Pressure High Temperature growth (HPHT)
HPHT growth - Answer- seed diamonds placed in chamber, flooded with molten carbon
and catalysts, imitates growth of natural diamonds, 1500 degrees C and 60,000 atm
pressure
Carbon Vapour Deposition (CVD) - Answer- flow H and CH4 gas through chamber with
plasma flame in flow path, low pressure, uses diamond seed crystal
Primary deposits - Answer- found in volcanic rocks on surface and un-erupted magmas
that feed volcanoes
Secondary deposits - Answer- include diamonds that have been moved from primary
source and concentrated in new location
Diamond growth - Answer- stable only at at least 150km below surface where pressures
are very high, need temperature between 900-1200 degrees
Archean Cratons - Answer- diamond window, stable part of the lithosphere at the centre
of many continents, 2.5 billion y/o
Kimberlite volcanoes - Answer- diamonds are generated at the base, magmas from
upper mantle pick up diamonds in their pathway, deposit on surface, must be rapid
Barren kimberlite - Answer- formed in non-diamond bearing regions
Indicator minerals - Answer- minerals in diamond bearing kimberlite (ex. green olivine,
purple pyrope garnet)
Lamprolite - Answer- rock type similar to kimberlite, hosts diamonds less often, derived
in mantle
Significant Lamprolite mine - Answer- Argyle Diamond Mine, Australia
Rarity of diamonds - Answer- due to the formation environments well below the surface
and the special conditions needed to transport upwards
,Lac de Gras area - Answer- NWT, first diamond-bearing kimberlite pipe, established as
Etaki mine in 1998, 3-5 million carats annually
Diavik Diamond Mine - Answer- officially opened in 2003, 8 million carats annually
Diamond cut - Answer- the quality of the facets that define its proportions, can have
significant impact on the shape of the stone
Diamond clarity - Answer- the internal and external imperfections of a stone, ranked
from I (included) to FL (flawless)
Common diamond flaws - Answer- solid mineral inclusions, fluid-filled inclusions,
clouds, feathers or external features (scratches, abrasions, burns)
Levels of clarity grading - Answer- Included (I1-3), slightly included (SI1-2), very slightly
included (VS1-2), very very slightly included (VVS1-2), internally flawless (IF), flawless
(FL)
Diamond colour - Answer- ideally colourless, scale ranges from D (colourless) to Z (light
yellow), anything beyond Z is fancy or fancy-intense
Diamond carat - Answer- 5 carats = 1 gram, 1 point = 0.01 carats, bigger stones are
more valuable
5th C of diamonds - Answer- country of origin, important to help understand possibility
of conflict zone
Diamond shapes - Answer- Cuts vary, some to intensify colours and some to maximize
brilliance and fire
Round brilliant - Answer- most common cut, based on physics to maximize light back up
through table of stone
GIA Diamond grading report - Answer- used to verify stone's quality, main physical
properties of graded diamond are clustered in small areas
Rapaport - Answer- most commonly used summary of the current diamond prices
Beryl - Answer- includes emerald and aquamarine, requires beryllium (Be, atomic
number 4), colourful, hard, often transparent, resistant to many acids, has the ability to
form large crystals
Emeralds - Answer- vibrant green, one of the most valuable gemstones, most
magnificent ones come from Colombia, require Cr3+
, Aquamarine - Answer- light to dark blue variety of beryl, most coveted colouration is
intense deep blue
Qualities of Beryl - Answer- usually forms in hexagonal prisms with flat "basal"
terminations, 7.5-8 hardness, colourless when pure, basal cleavage, uneven fractures
Ideal beryl formula - Answer- Be3Al2Si6O8
Emerald colour - Answer- when Cr3 substitutes for Al3
Aquamarine colour - Answer- when Al3 substitutes for Al3
Gota de Aceite - Answer- "Drop of oil" in Spanish, the name for emeralds of the finest
quality
Inclusions - Answer- other minerals being grown inside the parent mineral
Largest cut beryl - Answer- 2054 carats
Oiling - Answer- most common beryl treatment; oils with a similar refractive index to
beryl are forced into cracks of the stone
Heat treatment for beryl - Answer- brings out blues by turning Fe3+ into Fe2+, giving it a
light blue colour (aquamarine)
Synthetic beryl - Answer- produced commercially through hydrothermal solution, not
done for aquamarine because it is very common
Conditions for beryl growth - Answer- larger crystals need open space cavities or robust
growth within solid rock. Clarity needs stable, nurturing growth environment
Pegmatite - Answer- rare-element enriched igneous rock where beryl and its
Rare elements in pegmatites - Answer- lithium (Li), cesium (Cs), tantalum (Ta), niobium
(Nb), beryllium (Be), yttrium (Y), fluorine (F)
Structure of pegmatites - Answer- concentric (onion-like); boarder, wall, intermediate,
core
Where highest quality crystals are found in pegmatite - Answer- open space cavities or
pockets of core zone
Magmatic beryl growth - Answer- beryl either grows from grantic magma or is
transported via magmatically-driven hot hydrothermal fluids
