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GIA Diamond Grading

Lab Diamond Grading

QuestionAnswer
Name 3 methods of distinguishing internal from surface inclusions. Window and mirrors Focus and Depth of Field Reflected light
Does a callable clarity characteristic affect clarity? Yes as it can be observed under 10x magnification
Is non callable inclusion possible in a flawless diamond? Yes. Non callable does not affect clarity when observed over 10x magnification therefore can be found in a flawless diamond.
Name 3 categories of clarity characteristics Infernal External (aka Blemish) Surface reaching
When using windows and mirrors method where should you see a reflection when looking through a window? The opposing facet
If you observe a distance between characteristic and reflection what does this indicate? The inclusion is totally internal
No reflection when using windows and mirrors method indicates what? The characteristic observed is a blemish
Using windows and mirrors method what does a characteristic and reflection touching mean? Surface reaching inclusion is being observed
Reflection method shows a black characteristic what does this mean? Likely a surface reaching inclusion where it breaks the surface
What does the character in focus but surface out of focus indicate? Internal inclusion
Name 5 clarity factors Size Number Location Relief Nature
Name 3 reasons why we plot a diamond To ID a diamond To document condition @ the time of grading To support clarity grade
What is red marker used for in a plot? Most inclusions (internal)
What does red and green marker used together on a plot mean? Surface reaching Inclusion & Indicate a break to surface - etch channels, laser drill holes, knots, indented naturals or cavities
What does surface and character in focus indicate when using focal method? Nothing - it will not prove identity as it could be a surface reaching inclusion, blemish or internal inclusion so close to the surface it is indistinguishable.
In what order to we observe a diamond? Pavilion - girdle- crown
If a natural is confined to the girdle entirely without touching crown, pavillion or distortIng outline Is it non callable ? Yes only if this all applies.
Is an extra facet not observed under 10x in face up position considered callable? No it’s classed as non callable.
What are the 4 Cs known as? Value factors
Blemish is where on a diamond ? Confined only to the surface.
An inclusion is only internal No it can be a surface reaching inclusion as well
A brilliant cut has his many facets? 57/58
True or False When using a table gauge you need to estimate to nearest 0.05mm True
When adding up 4 table gauge measurements and dividing by 4 - is it ok to round the number? No do not round
AGD or Average Girdle Diameter is minimum diameter + max diameter divided by 2. Correct
Relief refers to contrast between inclusion and host diamond. This can impact on clarity grade. True. If the relief makes the inclusion more visible under 10x than a similar one with low relief it can lower grade.
True or false in relation to clarity factor an inclusion seen in the table area with 10x loupe the grade will be lower. True the table is the window to the diamond and usually clarity characteristics are more easily seen in this area.
Where do chips (a type of surface reaching inclusion) occur? Only on facet junctions, girdle edge or culet
True or false? A cavity is a surface reaching inclusion that occurs when a feather breaks away or a crystal drops or is forced out during polishing. True
A knot breaks the surface true or false? True
A pit and pinpoint both look like a tiny white dot. Which is considered a blemish? A pit is a blemish and is only on the surface.
What is the difference between a Nick and a chip? A Nick shows no depth at 10x loupe and a chip will show depth.
A dop burn can look white or transparent and is a result of manufacturing. True it is usually concentrated in a certain area.
Abrasion (Abr) A type of blemish it is a series of Minute scratches or pits. True
Green is used for plotting blemishes except extra facets True EF are plotted in black
Noting a bearded girdle is needed to support clarity grade of condition but is not plotted. True only in comments.
Created by: RachelHearne
 

 



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