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Labs Agree on Criteria for ‘Pigeon Blood Red’ and ‘Royal Blue’ Terms
Nov 5, 2015 10:52 AM
By Rapaport News
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RAPAPORT... Switzerland’s
colored-stone testing laboratories Gübelin Gem Lab and Swiss Gemmological Institute SSEF have
agreed on standard criteria for using the ‘pigeon blood red’ and ‘royal blue’ terms
as an increase in their usage had led to ambiguity and color “inflation.”
‘Pigeon blood red’ is now defined as a red color with no
apparent modifiers such as blue or brown, but a tiny purplish tint is
acceptable, according to a joint statement November 4. The hue has strong
fluorescence when exposed to ultraviolet light, resulting in an "inner
glow.” ‘Royal blue’ is described as saturated blue, either pure or with a slight
purplish tint.
The two terms can only be applied to rubies and
sapphires that exhibit “fine qualities” and have not undergone any color,
clarity modification or any type of treatment such as heating or fissure
filling, the statement pointed out. They must be relatively free of eye-visible
or dark inclusions and show a homogeneous color distribution with vivid
internal reflections.
Traders have traditionally used the two phrases to
describe high-quality rubies and sapphires, but without an agreement on the
criteria to define them, the groups explained.
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Tags:
colored stones, gemstones, Gübelin Gem Lab, Rapaport News, rubies, sapphires, Swiss Gemmological Institute SSEF
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