What is bicolor sapphire? Why the same stone is labeled differently depending on the identification organization
What is bicolor sapphire? Why the same stone is labeled differently depending on the identification organization
Bicolor sapphire is a sapphire that has two colors in one stone. We will explain the reason why the identification names are different, color zoning, and how to choose, based on an example in which the same 1.021 ct stone is described as "Pinkish Purple" by GIA and "Bicolor Sapphire" by Japan-German Gem Research Institute.
In conclusion
Even the same sapphireGIA's "Pinkish Purple Sapphire"、"Bi-color sapphire" at the Japanese-German Gem Research InstituteThe notation may be different.
This does not necessarily mean that one or the other is wrong. Even though the stone you are looking at is the same, it is likely that the stone is written differently depending on which characteristics are expressed in the name in the report.
In this article, we will explain Selby's 1.021 ct natural corundum based on the identification documents from GIA and Japan-German Gem Research Institute. The GIA report states that the sapphire was produced in Sri Lanka and has been heated, and the Japanese-German Gem Research Institute's identification report states that it is a bicolor sapphire and has been heated.
*This article is intended to provide gemological information and does not guarantee specific value, investment property, or future price. Descriptions regarding identification and processing are based on public information from GIA, Japan-German Gem Research Institute, AGL, etc., as well as actual identification documents obtained by our company.
What is bicolor sapphire? Why it looks two colors
Definition of bicolor sapphire: One stone has a primary color and a secondary color.
bicolor sapphirerefers to a stone in which two colors can be felt in one sapphire (corundum). Some colors appear clearly divided into two colors, such as pink and purple or blue and yellow, while others appear as if the nuances of the secondary color blend into the main color. The expression varies from stone to stone, ranging from sharp boundaries to those with gradations.
Why sapphire has two colors: crystal growth and trace elements (color zoning)
As sapphire's parent mineral, corundum, grows as a crystal, the amount of trace elements (chromium, iron, titanium, etc.) that give it its color may change. It is believed that this change remains in layers, creating "color zoning", resulting in multiple colors in one stone. GIA also explains that corundum exhibits color zoning due to changes in growing conditions.
The charm of bicolor sapphire: color boundaries and gradations
The real appeal of bicolor sapphire is that the appearance of its color changes moment by moment depending on the light and angle. The ability to enjoy two different expressions even though it is one stone, and the uniqueness that no two pieces are the same, attract many enthusiasts.
Sapphire is not the only gemstone with bicolor.
Bicolor tourmaline | A typical example where color bands appear due to crystal growth
GIA explains that in tourmaline, the concentration and composition of trace elements change during the crystal growth process, resulting in zoning such as bicolor, watermelon (red to pink in the center, green on the outside), and multicolor. The clarity of boundaries and the vividness of colors are factors in quality evaluation.
Ametrine | Amethyst and citrine coexist in the same crystal
Ametrine is considered a "bicolor quartz" in which the colors of amethyst (purple) and citrine (yellow) coexist in one crystal. The key points in appreciation and evaluation are determining whether it is natural or treated, and the clarity of the color boundaries.
Other bicolor gemstones | Also touch on cases such as fluorite
Fluorite and other products can also have multiple colors appearing in layers due to differences in the growth environment. Bicolor is not a phenomenon limited to specific gemstones, but can be said to be a universal beauty brought about by changes in the environment in which minerals grow.
Even with the same sapphire, there are stones that are "bi-colored" and stones that are not.
Stones with clear color boundaries / Stones that appear to blend together
There is a range of interpretation here, whether you see the color bands as ``two distinct colors'' or ``the main color mixed with the nuances of the secondary color.'' Stones with sharp boundaries are likely to be described as bicolor, while stones that blend together may be described as monochromatic + nuanced (for example, pinkish purple).
Why the impression changes depending on the cut and light source
Even in the same stone, the appearance of the two colors can vary greatly depending on the direction of the cut and the light source used for observation (natural light, white light, etc.). When evaluating colors by face-up, the direction in which you view them can affect the notation.
A judgment is made as to “to what extent should we evaluate the difference in color?”
In the end, we have to make a judgment on how far we should classify the colors as different. This is not an error, but a difference in how we think about color descriptions.
POINTWhether or not it is bicolor is a delicate topic that depends not only on the stone itself, but also on the direction in which it is viewed, the light, and the standard of description.
What is the difference between GIA and the Japan-German Gem Research Institute in terms of identification?
Features of GIA｜Include appearance color, processing, production area, etc. in the report
GIA (Gemological Institute of America) states that in its colored stone report, weight, dimensions, shape, cutting style, color, whether it is natural or synthetic, and any detectable treatments are listed in an organized manner, and information on the source (ruby, sapphire, emerald, etc.) will be added upon request. Color is determined based on hue, tone, and saturation under standard light source and facial expression. GIA calls the color “Pinkish Purple” for this actual stone as well.combination of huesIt is described in
Identification report from the Japan-German Gem Research Institute | This stone is listed as “bicolor sapphire”
The Japan-German Gem Research Institute (JGGL) explains that in addition to non-destructive testing such as refractive index, polarization, pleochroism, spectroscopy, fluorescence, microscopic magnification, and specific gravity, it combines analyzes such as ultraviolet-visible spectroscopy, FT-IR, and fluorescent X-ray component analysis to decipher the type, treatment, and origin of gemstones. It is one of the trusted institutions in Japan as a member of AGL (Association of Gemological Associations). This identification book from the Japan-German Gem Research Institute describes it as a "bicolor sapphire."
| point of view | GIA | Japanese-German Gem Research Institute (JGGL) |
|---|---|---|
| positioning | Widely adopted in international colored stone identification | AGL member/Domestic trusted organization |
| Main method | Color evaluation under standard light source, processing detection, and location of origin | Spectroscopy, FT-IR, fluorescent X-ray, magnified observation, etc. |
| This time's color notation | Pinkish Purple | bicolor sapphire |
Why do the same stones have different expressions? It's a "difference in perspective," not superiority or inferiority.
What is important is that there is no hierarchy of who is right and who is wrong. Even if the stones you are looking at are the same,“Which characteristics should I put into words?”The only difference is that For more details, see "Which is correct?" below.
[Example] GIA “Pinkish Purple” / Japanese-German “Bicolor Sapphire”
From here, we will compare the differences in the notation of each stone based on the two identification documents that Selby actually obtained.
Comparison of actual identification report data (Report number, Color column, Treatment column)
| Item | GIA (Sapphire Origin Report) | Japanese-German Gem Research Institute |
|---|---|---|
| report number | 1545442325 | No. J-1561xx (Management number 051425) |
| Publication date | January 27, 2026 | ─ |
| Weight | 1.02 ct | 1.021 ct |
| Measurements | 6.92 x 5.25 x 3.13mm | 6.91×5.24×3.13mm |
| shape/cut | Oval (Crown: Brilliant / Teibu: Step) | oval mixed cut |
| Species | Natural Corundum | natural corundum |
| Color column (Color) | Pinkish Purple | bicolor sapphire |
| Treatment | Heated | heating |
| Origin | Sri Lanka | (No description) |
*Slight differences in weight and dimensions (0.001ct, 0.01mm) are due to differences in measuring equipment and decimal processing, and both types of identification are for the same stone.
GIA: "Pinkish Purple Sapphire"
Japanese-German Gem Research Institute: “Bicolor Sapphire”
GIA Report 1545442325
Pinkish Purple Sapphire
It is described by a combination of hues as a sapphire whose main color has nuances of pink and purple. Produced in Sri Lanka, heated.
Japanese-German Gem Research Institute 051425
bicolor sapphire
Natural corundum. "Bicolor sapphire", described as heated.
A one-of-a-kind stone whose expression changes depending on the light and angle
This stone appears to alternate between pink and purple depending on how the light hits it and the angle you view it from. The two identification books can be said to be expressions of different ways of seeing the same stone in different ways. Exactly,How far should we consider color bands and overlapping colors as a single hue, and where should we begin to express them as two-color characteristics?This is a stone that allows you to feel the depth of gemstone identification.
*Heating treatment has been used for a long time to adjust the color and transparency of sapphires, and is a widely distributed treatment in the market. On the other hand, high-quality unheated sapphire is limited in distribution, so if it is of the same quality, it may be valued for its rarity and price.
In the end, which one is correct? GIA and Japanese-German differentiation
Q. Which is correct, GIA or Japan/Germany?
A. One or the other is not necessarily wrong.
In this example, GIA describes the exterior color as "Pinkish Purple," and the Japan-German Gem Research Institute describes it as "Bicolor Sapphire."
The same stone may be expressed differently depending on which characteristics are expressed in the name in the report.
In other words,Even if the stones you are looking at are the same, the only difference is “which features to describe in words”It is. It is recommended to understand them not as a hierarchical relationship, but as two different perspectives.
Points to consider when choosing bicolor sapphire
Clarity of color boundaries/beauty of gradations
The quality of appeal differs between those with sharp boundaries and outstanding contrast and those with smooth transitions. The stone you choose will depend on which one you prefer.
Balance between main color and secondary color
The impression changes greatly depending on the area ratio of the two colors and which one is the main focus of the cut. Stones with beautiful distribution and contrast of two colors are often highly valued as products.
“Another expression” that appears depending on the angle of light
The secondary color appearance that appears when you tilt the real thing is a charm that is difficult to convey in photos. If possible, we recommend viewing the actual item loosely.
Where can I read the identification book to tell the difference?
First, we check the gemstone type, then the color description, whether or not it has been heated or treated, and if necessary, the place of origin, weight, and dimensions. Especially in bicolorHow to write color notationThis reflects the individuality of each institution.
Summary | Enjoy bicolor not by its name but by its expression
The identification name is the entrance to the gemstone.
Both ``Pinkish Purple'' and ``Bicolor'' are just a gateway to understanding the stone in words. The real pleasure of bicolor is not to be confused by the different names, but to enjoy the ``color story'' behind it.
See unique colored sapphires at Selby
At Selby, we introduce sapphires and loose pieces with unique colors every day. Please take a look at the actual expression.
See the uniqueness of colors with your own eyes
A one-of-a-kind bi-color product whose expression changes depending on the light and angle. You can view it at the Selby official store.
View Selby's bicolor productsFrequently asked questions (FAQ)
◆ Basic knowledge
Q1. What is bicolor sapphire?
Sapphire is a stone with two colors within it. Some colors have clear boundaries, while others change like a gradation.
Q2. Why are bicolor sapphires created?
It is thought that color zoning is created when the parent mineral corundum grows as a crystal, and the way trace elements that are the source of color change.
Q3. Is it possible that the same sapphire is not written as "bicolor"?
there is. The expression on the identification report may change depending on whether you view the color band as two distinct colors or as a mixture of nuances of secondary colors in the main color.
◆ Differences in identification institutions
Q4. Why are the names different depending on the identification organization?
It is not a question of which is right or wrong, but rather a difference in how colors are described and how far they are categorized as "differences in color."
Q5. What does the GIA colored stone identification report include?
GIA officially informs us that it will provide information such as weight, dimensions, shape, cut style, color, natural or synthetic, detectable treatments, and country of origin upon request. (Source: GIA official)
Q6. What kind of tests are conducted at the Japan-German Gem Research Institute?
In addition to non-destructive inspections such as refractive index, polarization, pleochroism, spectroscopy, fluorescence, microscopic magnification, and specific gravity, the company explains that the type and composition of gemstones can be determined through analyzes such as ultraviolet-visible spectroscopy, FT-IR, and fluorescent X-ray component analysis. (Source: Japan-German Gem Research Institute)
Q7. Which is higher, GIA or Japan-German Gem Research Institute?
It's not a hierarchical relationship. GIA is widely used in international colored stone identification, and the Japan-German Gem Research Institute is one of the trusted identification organizations in Japan as a member of AGL (Association of Gemological Identification Groups). It is recommended to understand it as two different perspectives. (Source: AGL)
Q8. Can “pinkish purple sapphire” and “bicolor sapphire” be used for the same stone?
Yes, it can happen. In fact, the same stone that Selby acquired was described by GIA as "Pinkish Purple," "Sri Lanka," and "Heated," and the Japan-German Gem Research Institute described it as "Bicolor Sapphire" and "Heated."
◆ Rarity/asset value/price
Q9. Are bicolor sapphires rare?
Color zoning itself is a phenomenon seen in sapphire, but there are only a limited number of stones where the two colors are beautifully separated and can be clearly seen from the front. It is important to evaluate not only rarity, but also color distribution, vividness, transparency, and cut.
Q10. How should I think about the asset value of bicolor sapphire?
The value of a gemstone is comprehensively evaluated based on multiple factors such as color, clarity, cut, weight, treatment, and rarity. Bicolor's individuality is part of its value, but it does not guarantee future prices. When considering long-term ownership, it is important to check whether there is a reliable certificate of identification.
Q11. Is there a price difference between GIA and Japan and Germany for the same stone?
Although the identification document itself does not determine the price, the opinion of the place of origin (for example, Sri Lankan product), processing details, and the reputation of the identification organization can be used as a basis for making decisions when making a transaction. The quality of the stone itself is the center of its value.
Q12. What kind of bicolor is popular among collectors?
Items with a clear contrast between the two colors, high saturation in both colors, and unique placement of color bands tend to be popular. The real thrill of collecting is that ``no two items are the same.''
◆ How to choose/purchase
Q13. Will the value of heat-treated sapphires decrease?
According to GIA, heat treatment is a widely used treatment to adjust the color and clarity of sapphires. High-quality unheated stones may be valued for their rarity, but just because they have been heated does not necessarily mean they are of low value.
Q14. What are the points to consider when choosing bicolor sapphire?
The main points to check are the clarity of color boundaries, the beauty of gradation, the balance between primary and secondary colors, and the richness of expression that appears depending on the angle of light.
Q15. What kind of jewelry is bicolor sapphire suitable for?
Because it is a stone that enjoys contrasting colors, rings and pendants with bezels and open settings that clearly show off the face are popular. Many people choose to view the pieces loose or make them into jewelry at a later date.
Q16. How should I read the identification report?
First, we check the type of gemstone, then the color description, whether or not it has been heated or treated, the place of origin if necessary, and the weight and dimensions. In the case of bicolor, the individuality of each institution can easily be seen in the way the color notation is written.
Q17. Where can I buy bicolor sapphires?
Selby's official online store introduces sapphires and loose items with unique colors every day. You can take a close look at the actual expression.
View Selby's bicolor products ▸
View Selby's bicolor products ▸
Reference/source
- GIA (Gemological Institute of America) official website/Gem Encyclopedia (Sapphire, Tourmaline, Ametrine)
- Commentary on GIA “Color Zoning”
- GIA Sapphire Origin Report No. 1545442325 (primary document obtained by our company)
- Japanese-German Gem Research Institute (JGGL) official website/Explanation on identification technology, identification book No. 051425 obtained by our company (primary material)
- AGL (General Incorporated Association Association of Gem Identification Groups) Official Website