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GIA DIAMONDS AND DIAMOND GRADING
REVISION
London Diamond Syndicate - ANSWERS -What group was
critical to De Beers's early sales strategy?
Color - ANSWERS -How are gem-quality rough diamonds
sorted?
Baby Boomers - ANSWERS -What generation was first to
connect with diamonds as a representation of lifetime commitment?
India - ANSWERS -Where did the diamond industry first start?
Single-channel marketing - ANSWERS -What describes the
concept of centrally controlled supply, purchase, promotion, and sales of rough diamonds?
Lower mantle - ANSWERS -What mantle layer is most dense?
Will turn into graphite - ANSWERS -What happens to diamond if
lamproite stalls in the continental crust?
When a continental and oceanic plate collide - ANSWERS -
When does subduction occur?
High heat and high pressure - ANSWERS -How are
metamorphic rocks formed? CLIPPIR diamonds, blue diamonds, Brazil's Junia diamond -
ANSWERS -What is an example of a superdeep diamond?
A good sign that a pipe is nearby - ANSWERS -What might
black spinel in a mineral sample indicate?
Robotic/automated crawlers - ANSWERS -What equipment
might offshore deep-sea diamond mining use?
Primary deposits - ANSWERS -What deposit type produces most
diamonds mined today?
Character sampling - ANSWERS -What type of sampling gives
an initial idea of diamond quality for a deposit?
Brazil - ANSWERS -Where are rocks and geological structures
similar to Africa found due to ancient connections?
Crystal structure - ANSWERS -What is another term for crystal
lattice?
Type Ia - ANSWERS -What type are most natural diamonds?
Luster - ANSWERS -What term describes a gemstone's surface
in reflected light?
Fire - ANSWERS -What describes the flashes of spectral colors
seen in a polished diamond? Determine which proportion combinations create the most
attractive light performance - ANSWERS -What was the main
goal of research in developing the GIA Cut Grading System?
Measured btwn the normal and the reflected light - ANSWERS -
What best describes the angle of incidence?
Cleaving - ANSWERS -What process splits diamond rough along
its cleavage plane?
Strain - ANSWERS -What do cutters evaluate to determine
when to use a scaife for coning?
Bruting - ANSWERS -What made true round-shaped diamonds
possible?
Old European cut - ANSWERS -What was the prototype of the
modern round brilliant cut?
Holds/secures a diamond in place - ANSWERS -What does a dop
do?
High pressure, high temperature - ANSWERS -What does HPHT
stand for?
Cuboctahedrons - ANSWERS -What rough form does NOT
appear in natural diamonds
Type 1b - ANSWERS -What diamond type can be created by the
HPHT method?
CVD lab-grown diamonds - ANSWERS -What diamonds have
strain pattern and intensity similar to natural diamonds?
At every step - ANSWERS -When should the origin of a lab-
grown diamond be disclosed?
Internal laser drilling - ANSWERS -What diamond clarity
treatment expands inclusions?
Annealing - ANSWERS -What diamond color treatment further
modifies color by allowing vacancies and trace elements to diffuse post-irradiation?
Graphitization - ANSWERS -What describes the formation of
graphite around a diamond's mineral inclusions and feathers?
Sharpens spectral absorption peaks and allows gemologists to
identify the optical defects in the diamond - ANSWERS -What
does cooling a diamond do to spectral absorption peaks? A diamond's absorption of visible light, portions or UV light and
infrared regions close to the visible range - ANSWERS -What
can UV-Vis-NIR spectroscopy help identify?
Terms of payment - ANSWERS -What is an agreement that
involves multiple payments over time?
$20,000 - ANSWERS -What is the per-carat price of a 2ct
diamond selling for $40,000?
Pick price - ANSWERS -What parcel price comes at a premium?
Per-carat price - ANSWERS -How do dealers quote diamond
prices?
Inclusions - ANSWERS -What is the term for flaws or
imperfections in a diamond?
Loupe/microscope - ANSWERS -What can help determine a
clarity characteristics location?
Blemishes - ANSWERS -What clarity characteristic is found only
on the surface of a gemstone?
Cavity - ANSWERS -What clarity characteristic results when a
crystal is expelled?
Directly under the table - ANSWERS -Where are inclusions most
visible?
Cloud or pinpoint - ANSWERS -What kind of clarity
characteristic is not seen at 10x mag.?
Relief - ANSWERS -What describes the contrast btwn an
inclusion and the diamond? Noticeable inclusions that are very easy to see at 10x mag. -
ANSWERS -What best describes the clarity characteristics in
SI1 and SI2 stones?
Plotted on both the crown and pavilion diagrams - ANSWERS -
Where is a feather that reaches both the crown and pavilion plotted?
Degree of darkness or lightness - ANSWERS -What is a term
that describes tone?
Gray - ANSWERS -What color becomes more prominent as cool
hues become less saturated?
Paying for more weight than you see - ANSWERS -Why do
diamonds with thick girdles offer less value?
Misshapen facets - ANSWERS -What might be found in a
diamond with misalignment (Aln)?
Make it look foggy - ANSWERS -How do shallow pavilion angles
affect appearance?
Mixed cut - ANSWERS -What style describes a diamond that
has both brilliant-cut and step-cut facets?
Shoulders - ANSWERS -What is the area between the head and
belly of an oval?
Width of stone (instead of average girdle diameter) - ANSWERS
-What is used for total depth percentage calculation in fancy shapes?
Too many variations - ANSWERS -Why is there no single cut
grading standard for fancy cuts?
French tip - ANSWERS -What style helps avoid point breakage
in fancy cuts?
2:1 - ANSWERS -What is the length-to-width ratio for a fancy
cut 4.00mm long and 2.00mm wide?
Mathematical formulas - ANSWERS -How do diamond
professionals estimate the weight of mounted diamonds?
Single grade - ANSWERS -What do appraisers assign to larger
mounted diamonds when color grading?
Improvable - ANSWERS -What term describes a diamond whose
clarity can become VVS after repolishing? Remove color zoning (rarely used) OR increase color -
ANSWERS -What is a good case for recutting?
Bourse - ANSWERS -A diamond buying and selling club (they
have them in trading centers)
Peridotite - ANSWERS -A type of rock that diamonds form in
- igneous rock (formed from a molten state)
- most diamond form in this rock
- has consistent release of carbon
Eglogite - ANSWERS -A type of rock that diamonds for in
- metamorphic rock (rocks that have been altered by heat and pressure)
- does not have a consistent release of carbon
3.52 - ANSWERS -What is the specific gravity of a gem-quality
diamond?
Marine deposits - ANSWERS -Diamonds are more concentrated
in which type of deposit?
Look for the oldest parts of the earths crust - ANSWERS -The
first step in exploring for diamonds is to _____ The world's supply of diamond rough has increased (more
diamonds are available to people) - ANSWERS -The diamond
industry has changed dramatically in recent years because _____
India - ANSWERS -The Argyle mind in Australia contributed to
the rise of the cutting industry in _____
Dodecahedral - ANSWERS -What is the softest crystal direction
in diamond?
Isometric or cubic crystal structure - ANSWERS -What crystal
structure does diamond belong to? Cubic (runs horizontal), octahedral (on face), dodecahedral (runs
vertical) - ANSWERS -What are diamond's 3 internal crystal
planes?
Octahedral planes - ANSWERS -The crystal planes most
suitable for cleaving a diamond are the _______ planes?
Isometric - ANSWERS -Another name for the cubic system
Blocker - ANSWERS -Polishes the crown and pavilion mains
Brillianteering - ANSWERS -Polishing of the star and upper and
lower half facets
Kites - ANSWERS -Bezel facets are the ones shaped like ____
Triangles - ANSWERS -Star facets are the ones shaped like
_____ next to the table
Outer edge - ANSWERS -Upper half facets are the ones on the
______ next to the girdle
Radiant energy - ANSWERS -Visible light is a form of
More light leakage through the pavilion - ANSWERS -Grease on
the pavilion of a diamond results in
Allowing for greater weight retention from rough - ANSWERS -
The rotary saw contributed to the diamond cutting industry by
The five clarity factors - ANSWERS -Size, number, location,
relief, nature
Requirements for a Flawless diamond - ANSWERS -No
inclusions or blemishes under 10x can have these features:
- extra facets not visible face-up
- naturals confined to the girdle as long as they don't thicken the girdle or distort its outline
- internal graining that's not reflective, white, colored, and doesn't affect transparency
- inscriptions that don't penetrate the surface
Requirements for a VVS1 and VVS2 - ANSWERS -Contain
minute inclusions that are difficult to see under 10x VVS1:
- inclusions are extremely difficult to see face-up; pinpoint or two, possible internal graining not seen face-up VVS2:
- inclusions are very difficult to see; surface-reaching inclusions possible
Requirements for a VS1 and VS2 - ANSWERS -Contain minor
inclusions that range from difficult (VS1) or somewhat difficult (VS2) to see at 10x
- all inclusions are possible, grade depends on overall visibility
Requirements for a SI1 and SI2 - ANSWERS -Noticeable
inclusions that are easy (SI1) or very easy (SI2) to see at 10x
- all inclusions are possible, grade depends on visibility
Requirements for I1, I2, and I3 - ANSWERS -Inclusions are
obvious at 10x but can be seen without magnification
- inclusions seriously affect durability
- usually used for industrial purposes
What do the colors on a plot mean? - ANSWERS -Green -
blemishes Red - inclusions Red and Green - cavities, indented naturals, knots, etch channels, laser drill holes Black - metal work from setting
Diamond types - ANSWERS -Ia: abundant, plentiful nitrogen;
near-colorless to yellow Ib: rare, less nitrogen than Ia; more yellow than Ia IIa: very rare, little to no nitrogen; colorless, brown, or gray IIb: very rare, contains boron, little to no nitrogen; blue
Tone - ANSWERS -The relative lightness or darkness of a color
Saturation - ANSWERS -A color's strength or intensity (ranging
from dull to pure vivid)
Hue - ANSWERS -The basic color of an object
Use the bowing method; If the lines bow out slightly, the table %
is about... - ANSWERS -63%
Use the bowing method; If the lines bow out noticeably, the table
% is about... - ANSWERS -67%
The flash method - ANSWERS -Used to estimate table %
- simplest and quickest method but need experience looking at lots of different table sizes
- Small flash = table % less than 60%
- Medium flash = table % is 60-64%
- Large flash = table is 65% or more
The ratio method - ANSWERS -Used to estimate table %
- imagine a line from girdle to star facet (line A) and a line from star facet to center of stone where culet is (line B) *A is always 1
- 1:1 = 54%
- 1:1 1/4 = 60%
- 1:1 1/2 = 65%
- 1: 1 3/4 = 69%
- 1:2 = 72% Use the ratio method; If lines A and B are 1:1, the table % is
about... - ANSWERS -54%
Use the ratio method; If lines A and B are 1:1 1/4, the table % is
about... - ANSWERS -60%
Use the ratio method; If lines A and B are 1:1 1/2, the table % is
about... - ANSWERS -65%
Use the ratio method; If lines A and B are 1:1 3/4, the table % is
about... - ANSWERS -69%
Use the ratio method; If lines A and B are 1:2, the table % is
about... - ANSWERS -72%
What are the methods used for table size/table % estimation? -
ANSWERS -- the flash method
- the ratio method
- the bowing method What are the methods used to estimate crown angle? -
ANSWERS -- Profile method (looking at the profile and
estimating the angle)
- Face-up method (using the width of the pavilion mains through the table) Excellent cut grades corresponding total depth % is... -
ANSWERS -57.5-63%
