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Evaluation of sapphire: color, weight, clarity

Evaluation of sapphire: color, weight, clarity

June 24, 2021

Evaluation of sapphire

In the photo: blue sapphire nearly 20 ct, Sri Lanka

Sapphire is a precious stone, corundum mineral variety. They are considerably rare and since ancient times have been highly appreciated. We we are accustomed to blue color of this stone, but few know, that they can also be of almost any color: yellow, pink, purple, green, etc. These varieties are referred as fancy or multi-colored. Corundum of red color are named as ruby. In this article we tell about features of classic blue corundum. It decorates famous royal jewelry and tends to rise in popularity in modern jewelry all over the world. How to choose and buy successfully a high quality sample? Let’s look.

Color

First of all, color of sapphires affects its beauty. The following colors are typical for “classic” sapphires: blue, light blue, and also with violet or a greenish tint. The best specimens have a bright blue color without additional shades. In international trade there are two commercial colors: “Royal Blue” and “Cornflower Blue”. Royal Blue is considered one of the most expensive. It is the best color for asian region where is no lack of sun at almost any time of the year. Connoisseurs from Northern countries less like Royal blue color due to the poor lighting outdoors and indoors, because stones will often appear almost black. That is why some people prefers lighter tones. For example, «Cornflower blue», that resembles cornflower flowers. It is also a high valued color. For such cornflower samples the presence of “silkiness” and a kind of «internal glow» are typical. This is due to the content of a large amount of whitish needle inclusions of rutile, which reflect light. Untreated sapphires of “cornflower-blue” color, mined in Kashmir, are considered the most expensive in the world.

Sapphire color

In inexpensive jewelry you can find dark, almost black sapphires, which are usually the cheapest options on the market. Such stones cannot be compared with the best light-blue and velvet blue. Too light samples are also less valued. Some samples display a color change effect. For example, in daylight, a sapphire shows blue, and by incandescent light it shows purple shade.

In the photo: saturated sapphire (a left pair) and very dark color (a right pair)

Choosing sapphires pay attention to the distribution of color whiting a stone. For many sapphires color zoning is typical, which looks as alternating light and dark stripes, located at an angle of 120 degrees. Sometimes color is distributed in a stone as stains. It is necessary to take into consideration zoning and to orient a stone by a way to make zoning less noticeable when a person views a stone face-up (table up).

“Practical advice.  How to choose a sapphire which will not lose in price over time? The most important element in choice is an assessment of a color, you should like it. It is better to look at a stone in different types of lighting: in daylight on a street or near the window, and under various lamps. Keep in mind, that in some white light fluorescent lamps violet shade in blue sapphires, reducing their cost, can become invisible. Also pay attention, whether a stone is light or dark, whether a color is saturated or not. Is a zoning evident when you view a stone table up? Note, if a sapphire sample seems dark, or even slightly dark, then in poor light it will look almost black and “play” bad. In daylight sapphires are looking the best of all. Choose bright stones. “

Clarity

In addition to color of sapphires, their clarity influences on beauty: amount of inclusions and cracks, and how much they are visible to the naked eye, or when looking at a 10-fold gemological loupe. Sapphires are characterized by the presence of light needle-like rutile crystals, which sometimes can create the effect of “silkiness” in a faceted stone. Fingerprints and solid inclusions may also present. Presence of inclusions not always affect beauty perception, if they are not contrast, not large and if they are not strongly striking. If a sapphire has very bright beautiful blue shade, which is usually rare, you can look on clarity not very strictly. If the stone has an ideal clarity, it can be either very rare and expensive natural sapphire or synthetic sample, grown by the cheapest method. For such high clarity samples it is better to ask a seller to give a certificate from an independent gemological laboratory, which will confirm natural origin. Sapphires with low clarity, opaque stones are usually cut in cabochon form.

In the photo: a bright blue sapphire from Madagascar, 3.42 ct. It has colorless crystal inclusions all over the stone, that are not influenced on its beauty.

Sapphire clarity

“Practical advice. How to choose a sapphire sample with good clarity? Before clarity evaluation be sure that a surface of a stone is clean and doesn’t have dirt or dust. Firstly look at a stone with a naked eye. Are large cracks or inclusions very noticeable? It is desirable that they are not in the center. See if inclusions and cracks greatly affect overall attractiveness? Then, you can look at the stone in a 10x magnifying loupe for a more comprehensive analysis. In this case, pay attention to whether large cracks in the stone go to its surface or not. The presence of such cracks can lead to the shattering of the stone, even from an accidental impact. “

Carat weight

Cost of a sapphire significantly rises with an increase of it weight. The reason is a rarity of large samples. Nowadays you can hardly find gem-quality blue corundum weighted over 5 ct.

very rare high quality untreated blue sapphires from Sri Lanka

In the photo: very rare high quality untreated blue sapphires from Sri Lanka weighted over 30 ct each

“Practical advice. How to choose a sapphire of necessary size? You can roughly estimate how the stone will look being fixed in a jewel. To do this, put it on top of your fingers. Move your palm in different lighting and pay attention to the attractiveness of the stone as a whole. Do you like it or not?“

On the video: judgment of overall attractiveness in different light. Violet tint is noticeable in incandescent light.

– In the second part of the article we consider such quality factors as cutting of sapphires, enhancement and certificate, and we tell about varieties.

– In the third part of the article we show you real prices per carat on blue sapphires.

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