When talking of pink corundum, where does one draw the line between
the paler, pinkish rubies and pink sapphire?
Pink Sapphire or Pale Ruby? by Ted Themelis
One of the most controversial and still unresolved issues for the
gemological community is the appropriate definition of, or
relationship between, pink sapphire and ruby. Generally, in the
marketing of color designations of ruby and pink sapphire
tend to refer to rubies as gems that are medium to dark red to orange
or purplish-red and to pink sapphires as pale to light red. Both
gemstones are, of course, color varieties of corundum.
The issues.
The question of definition arises because of three major issues:
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Whether or not pink sapphire should be considered as an individual
color variety of corundum.
-
If each color variety is to be considered separately, at what
point the demarcation line between ruby and pink sapphire occurs?
-
What are the proper lighting conditions to be used to determine
their exact color?
Gemstone dealers and jewelers have argued on these issues for years.
The goal of many dealers is to buy the gem as pink sapphire and sell
it as ruby, because in most cases rubies are considered more valuable
than pink sapphires and therefore produce more profit.
Historical aspects.
Before any attempt would be made trying to resolve this problem, it
might be wise to look at the historical aspects of the issue. Max
Bauer, in his Precious Stones (1896), gives the following definition
of ruby:
“The tone of color (in ruby) differs in different specimens, being
sometimes deep and intense, sometimes pale and light. The lighter
shades vary from pale rose-red to reddish-white, some specimens being
so faintly tinged with red as to appear almost colorless. The darker
colors are pure red, carmine-red, or blood-red; the red of the
majority of rubies, however, has a more or less distinct tinge of
blue or violet, this being specially noticeable in transmitted light.
The shade of color most admired is the deep, pure carmine-red, or
carmine-red with a slight bluish tinge.”
A few years later (1909), Julius Wodiska describes ruby in his Book
of Precious stones:
"The color-tone of the ruby varies greatly, and the presence of
deep, intense tones of red causes the term 'masculine' to be
applied to a gem while the paler tints suggest the term
'feminine.' Rubies range from a delicate pink tint through pale
rose-red to reddish-white, pure red, carmine red, or blood red. A
tinge of blue or violet is frequently discernable in these
shades."
So, here we have introduced the designations “masculine ruby” and
“feminine ruby”! Although the term “pink sapphire” has not been
mentioned so far, there is an indirect attempt to separate the deep
red corundum’s (“masculine”) from “feminine” rubies, the lighter red
corundums. Some speculation has it that the “feminine” ruby
represents Sri Lankan material, while “masculine” ruby represents
Burmese or Thai material. Obviously, such designations were devised
to emphasize the existing differences between “masculine” and
“feminine” rubies and to prevent potential misunderstandings.
Early reference to pink sapphire in gemological literature is given
by G.F. Herbert in the sixth edition of Gemstones (1930):
"The tint of the red stones varies considerably in depth;
jewelers term them, when pale, pink sapphires, but of course, no
sharp distinction can be drawn between them and rubies."
From that time until now, the designation “pink sapphires” has
appeared in every gemological publication. Reference to it is made,
for example, even by R.M. Shipley in The Dictionary of Gems and
Gemology:
"Ruby. The red variety of corundum. Intense, medium to medium
dark purplish red (so-called pigeon's blood) is best, intense red
is fine, and dark red is less desirable. Star ruby is rare. In
the jewelry industry, the finest purplish-red stones, principally
from Burma, are known as 'Burma,' or 'oriental rubies'; less
valuable, darker red, principally from Thailand, as 'Siam
rubies'; and light red, from Ceylon and elsewhere, as 'Ceylon
ruby' or pink sapphire."
R.Webster describes ruby in his monumental Gems (4th ed.,1983) as
follows:
"Ruby varies in shade from a pale rose tint through all shades of
red to a deep crimson sometimes known in the jewelry trade as
'black.' The pink colored corundum may be considered as a pale
ruby but a pure pink colored stone is known as pink sapphire, all
fancy colored corundum's being termed sapphire with the color as
prefix. The decision whether a stone is pink sapphire or pale
ruby may often lead to debate."
Discussion.
The need to define ruby specifically as a color variety of the gem
species corundum is obvious, whether the material is called
“masculine ruby”, or “oriental ruby”, or “Sian ruby”, or anything
else. Yet one side in the debate over names argues that since pink
sapphire is light red - rather than a different color completely -
there should be no distinction made between ruby and pink sapphire at
all. In fact, the Asian Institute of Gemological Sciences (AIGS) in
Bangkok, Thailand, has abandoned the use of the pink-sapphire
designation (as an individual variety of corundum) from its
educational programs, as well as from the gem-identification reports.
The opposing side argues that pink is an entirely separate color
designation from red, with the “separation line” between pink
sapphire and ruby precisely defined. Those who adopt this position
argue that a distinct classification of pink sapphire as an
individual variety of corundum is sound, since designations for other
separate categories of sapphire, such as “orange” and “purple”
sapphire, do exist and are necessary.
Color grading.
The need for a universally accepted and practically workable color
grading system for gemstones is obvious and will resolve many
problems including the “ruby or pink sapphire” issue. In the past,
several color grading system have been introduced, consisted from a
series of “master” reference points -in the form of a set of color
chips, or chart of color samples, or a tri-dimensional substance that
silulates a gemstone. However, in practice, they never meet the
strict criteria of proper gemstone color grading.
It is the author’s opinion that, the color-grading problem may be
solved using C.I.E. chromaticity coordinates emanating from
spectrophotometer readings. Representing the tristimulus values of
the visible color spectrum, these readings should be the basis of
fabricating a tri-dimensional object that will simulate a
“reference-point gemstone” that may be called master. These masters
shall be fabricated from suitable material taken into consideration
transparency, luster, refractive index, fluorescence and all other
appearance attributes characteristic to ruby and pink sapphires.
Since it is impossible to produce all the colors of ruby and
sapphire, the best method is to fabricate sufficient number of
masters that represent the most frequently occurring colors and
appearance in ruby/sapphire based on their country of origin.
Thus, direct comparison between the color of the gem and the “master”
is possible. Series of these “masters” may consist of a so-called
“color matching system”. Certain number of these “masters” may
represent a range designated as an individual variety (pink sapphire)
of corundum, while other masters may represent the ruby designation.
There should be a “master” that would represent the “transition
point” - that is, the cut-off point that separates pink sapphire from
ruby. Thus, pink sapphire may be defined as having less that 50% of
the color component needed for a gemstone to qualify as ruby.
Lighting conditions.
Equally important, is the need for a standardized and universally
accepted light source. The apparent color of rubies and pink
sapphires is, to some degree, influenced by fluorescence stimulated
by ultra-violet rays of sunlight. Thus, rubies and pink sapphires
appear different in Southeast Asia from how they do in locations in
the Northern Hemisphere, say New York or London. But, in reality, to
persuade Sri Lankan and Thai dealers to use a designated light source
will be a nearly impossible task. A suitable light source for proper
color grading should have the following spectral properties:
Color Temperature above 5,500oK
Color Rendering Index (CRI) above 90
Harmonic spectral distribution in the ultraviolet and visible region
of the e-m spectrum.
There are several lamps readily available in the market that meet
above criteria. Try the 18" long “Vitalite” by DuroTest Company, or
“Daylight-99” by Mitsubishi.
NOTE: Please refer to page 19-20 of my book “The Heat Treatment of
Ruby & Sapphire” for full discussion on lighting sources.
The effect of heat-treatment.
A final comment on this issue should center on the effect of
heat-treatment on pink sapphires and rubies. The author has
successfully performed many experiments on removing the purple and
brownish-overcast color from rubies and pink sapphires. The results
were very interesting, especially when the color fell on or about the
transition point: On some rubies, the removal of purplishness
produces a purer, lighter-red coloration that prevents the substance
from being considered ruby any longer, but it appears as pink
sapphire. The paradox was that although the value of the ruby should
have being increased as a result of the removal of the undesirable
brownish tinge, its actual value may be decreased (or remained the
same), because the stone is considered by many dealers as pink
sapphire.
Since problems like this persist, the author wishes to salute
organizations, as well as various individuals in the gemological
community, who actively raise questions about the whole issue and
seek to provide solutions. So far, unfortunately, apathy on the part
of various trade, jewelry, and educational organizations blocks a
sound solution from being accepted.
Yet, the issue does need to be resolved. With prices of gemstones
escalating rapidly, the game of “buying pink sapphire and selling it
as ruby” needs immediate attention. (The same game could easily occur
with other gemstones as well: “buy it as green beryl; sell it as
emerald.”) If a cure is ever finally offered by the jewelry industry,
I simply hope that the solution chosen won’t ultimately be worse than
the “disease” itself!