Assignment 8 - Color Flashcards
What are the three components of bodycolor?
- Hue
- Tone
- Saturation
How does the trade use special terms to describe gem color?
Trade terms connect certain words with particular gemstone colors or geographic locations.
The selection of colors in which a gemstone occurs.
Color range
The color or colors in a gemstone’s color range considered by the trade to be the most desirable.
Fine color
A gemstone’s basic color, determined by its selective absorption of light.
Bodycolor
The first impression of an object’s basic color.
Hue
Degree of darkness or lightness of a color.
Tone
A color’s strength or intensity.
Saturation
Terms often used in the jewelry industry to describe particular gemstone colors or link gems with specific geographic locations.§§
Trade terms
How does a gemstone’s cut influence its face-up color?
Every piece of rough has its own unique pattern of color distribution, which is the amount of color
and its location in the crystal.
What causes windows?
Shallow cutting results in loss of light. Light entering the stone’s crown from above meets the pavilion facets at the wrong angle and exits the stone without being reflected back to the eye. And because the pavilion is shallow, light from below travels through the pavilion and exits through the crown. Because the light has only a short distance to travel through the stone, the color is less intense than if the stone were cut to excellent proportions.
What causes extinction?
Extinction is a result of the cutting process, and all stones display some extinction at some viewing angles. Light enters the crown facets, reflects off one side of the pavilion, and escapes through the other side of the pavilion instead of through the crown.
How do color zoning and pleochroism influence a gem’s color or appearance?
Depending on how the gems are cut they might have a visible impact on the color of the gem and influence its value.
How does clarity affect a stone’s color?
Fine inclusions can scatter light within a faceted
stone and make extinction much less noticeable. Stones with a slightly diffused, or “sleepy,” appearance, like some sapphires, show this effect. Inclusions can also give a gem its color. Bright particles of green mica give aventurine quartz its green bodycolor, and inclusions of brownish hematite add depth to the color of some yellow sapphires.
How does fluorescence affect a stone’s color?
Fluorescence adds an extra glow to red spinel’s appearance. It also boosts the red bodycolor of chromium-rich rubies, sometimes enough to
counteract extinction.
An area of weak saturation in a transparent gemstone’s bodycolor that usually results from
the way the gem was cut.
Window
Dark areas in a faceted transparent colored stone.
Extinction
Light that exits through the pavilion in an
uncontrolled way due to compromises in a gem’s proportions.
Unplanned light leakage
Light that exits through a gem’s crown in a
controlled way due to the correct proportions of its cut.
Planned light leakage
Areas of different color in a gem, caused by variations in growth conditions.
Color zoning
Visible face-up color zoning that the cutter
was unable to conceal.
Unintended color zoning
Visible face-up color zoning that was planned during the cutting process.
Intended color zoning
What should you look for when judging a gem’s color?
- Is the stone light, medium, or dark in tone?
- What is the gem’s bodycolor?
- Is the saturation weak, moderate, strong, or vivid?
- Is the stone’s color exceptional or poor for that gem species?
What conditions are important for effective color grading?
One of the most important aspects of buying and grading colored stones is the type of lighting you use. For consistency, you should view colored
stones under daylight-equivalent fluorescent lighting whenever possible.
What steps should you take to grade a colored stone?
- Clean Stone
- Hold against white/neutral background
- Evaluate the tone
- Assess bodycolor and identify hue.
- Consider the saturation
