3 - Color and Value Flashcards
Near-colorless
G-J
Colorless
D-F
Faint
K-M
Very Light
N-R
Light
S-Z
Normal color range
D-Z, colorless to light yellow, brown, and grey
Of the color components hue, tone, and saturation, what does the GIA scale describe?
Tone and saturation
Depth-of-color
The combination of tone sand saturation that determines how noticeable a color is.
How do mountings affect apparent color?
A complimentary mounting can make stones in the G-I range appear colorless. GIA does not grade mounted diamonds.
What range appears nearly colorless to the naked eye?
J-L
At which grade will an individual start to see color to the naked eye?
Beyond M.
Masterstones
a set of color comparison diamonds that defines GIA’s color grades in the normal range.
What are the three factors that consistent color grading depends upon?
1) Masterstones
2) Environment
3) Grader
When is it appropriate to use “color memory” to grade?
Never. Always compare with a set of masterstones.
Where are color differences more visible?
Subtle differences are more visible through the pavilion, so the color is graded table-down.
What are the best colors for your lab?
Neutral grey, white.
How do you obtain proper lighting for grading color?
Use steady fluorescent daylight bulb.
How can a grader be at their top game?
Stay up to date on training, maintain good health habits.
Fluorescence
Emission of visible light by a material when exposed to UV radiation.
Ultraviolet (UV)
Light wavelength that’s invisible to the human eye.
In what % of diamonds can you see fluorescence?
About 35%
In what colors does fluorescence manifest?
Blue is most common, possibilities include white, yellow, and orange.
How can fluorescence enhance a gem?
Blue fluorescence can mask yellow color.
How can fluorescence detract from a gem?
Too strong fluorescence might make a stone look cloudy or oily.
Colored diamonds
Yellow, brown and gray diamonds with more color than the Z masterstone; OR diamonds that exhibit any other color face-up.
How does the value change as the color deepens in a colored diamond?
The value increases as the color deepens.
What are the least common colored diamond colors?
Red, green, purple, and orange.
What are some of the middle-rarity colored diamond colors?
Pink, blue
What are the most common colored diamond colors?
Yellow, brown, black, milky. Less valuable than other colored stones
Describe a colored diamond’s usually depth-of-color.
Saturation often low, muted with grey/brown, or blended with other colors.
What is the key difference in grading colored as opposed to “normal” diamonds?
Evaluate face up to better assess hue, tone, and saturation.
Characteristic color
The basic face-up color of a colored diamond. Excludes surface reflections, fire, and dark or washed-out areas
What final color grade for a colored diamond apply to all colors except yellow?
Faint, Very Light, Light
Name 5 depth-of-color grading terms.
Faint
Very Light
Light
Fancy Light
Fancy
Fancy Intense
Fancy Vivid
Fancy Dark
Fancy Deep
Color treatment
A way to alter or add color by coating, irradiation, heating, or a combination of the latter two.
Coating
Super-thin layers of chemicals applied to a few of the pavilion facets, or to a tiny spot on the culet or around girdle.
Where is a coating usually applied?
Pavilion facets, a spot on the culet, or around the girdle.
How can one detect a coating?
Visually, the color may be unusual and difficult to classify. Can also be confirmed under a microscope.
Can coatings be removed?
Yes, even polishing can remove a coating.
Irradiation
A treatment that changes the color of a gem by exposing it to radioactive materials by changing the crystal structure of the diamond.
Annealing
A gemstone heating process that can be used alone or to stabilize irradiated color.
Fracture filling
Doesn’t change actual color and apparent will change if filling material removed or damaged.
HPHT
A combination of high pressure and high temperature to lighten, remove, or create color.
How light can HPHT make a diamond?
D-H
Which kinds of treated diamonds with GIA grade?
Anything considered permanent (HPHT, Irradiation)
What are the Two Rs when selling color?
Rarity and romance
What do rarity and romance describe with respect to the Two Rs?
Rarity will explain value, romance will sell a diamond’s ethos.
