Diamonds
The Colour of Diamonds
Hue: Pure, spectral (prismatic) colour.
Hues include gradations and mixtures of red, orange, yellow,
green, blue, violet, and purple.
Tone: A colour's position on a colourless-to-black
scale.
Saturation: A colour's position on a neutral-to-vivid
scale.
Fancy diamond: A diamond with an attractive
natural body colour other than light yellow, light brown,
or light gray.
Treated diamond: A diamond with body colour
bodycolour induced by some form of artificial irradiation,
often in conjunction with controlled heating (known as annealing).
Coated diamond: A diamond coloured by a
surface coating which masks the body colour bodycolour; the
coating may be extensive (entire pavilion, for example), but
is more often limited to one or two pavilion facets or a spot
on the girdle.
Detecting Treated Diamonds
Treatment Clues: Even, medium to dark, vivid green, blue-green,
or blue body colour.
Treatment Proofs: Umbrella effect, coloured
pattern following facet junctions, coloured ring around the
girdle (green, yellow, brown, pink); radioactivity (radium
green); brown, disc-like inclusions (radium green); fogs photographic
film (radium green); electrically non-conductive (blue); 592
nm absorption line (green, yellow, most brown, pink).
Natural Clues: Darker green or brown naturals
or surface spots (light green, brown).
Natural Proofs: Electrically conductive
(blue).
When in doubt, always submit coloured diamonds to GTL for
an origin of colour report.
Detecting Coated Diamonds
Examine the surface under high magnification (45x or more)
in diffused or reflected light. Pay particular attention to
areas near the girdle. The coating may have tiny pits or bubbles,
and may be scratched with a probe; an orange filter may help.
Other clues include subnormal brilliance and dispersion, an
iridescent sheen or a lack of transparency when viewed table-down
in the DiamondLite, or an odd look when compared to masterstones.
ColourMaster
Use the colourMaster to:
- create objective colour descriptions
- establish reliable price comparisons
- make exact records of coloured diamonds, bought, sold,
or appraised
- communicate more effectively and confidently with suppliers
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