A natural sapphire is a variety of corundum that has blue hues. Stones with colors other than blue and blue are categorized as fancy sapphires, such as yellow, pink, purple, padparadscha, green, or colorless. The cost of blue-colored sapphires increases greatly with the weight of the stone. This is because large-size crystals are mined very rarely.
The color palette of transparent blue sapphires varies widely. One can find blue and blue colors of different saturation. There are also examples of blue-violet and blue-greenish hues, but the most valuable and rare stones are those with the same bright blue color.
The most rare and expensive varieties of blue natural sapphires are:
Cornflower Blue sapphire are "silky" in color and have a faint inner glow. These properties are due to the presence of rutile inclusions, which reflect light rays. The reference point is the blue cornflower blossom, but for sapphires it is the whole range of colors, from bright blue to bright blue, but not dark at the same time. It is important to note that on the Russian market, it is the cornflower-blue color that is more suitable than the royal blue. The reason is that there are so many cloudy days that "royal blue" sapphires in our zone can look dark and lose their charm, unlike in Asia, where they look very expensive and aristocratic.
Peacock blue, the color of the bright blue of a peacock's neck or the feathers on its tail, is a bright blue color found in sapphires from Sri Lanka; another name for this spectacular color is "electric blue. Not all of the world's laboratories place this color in a separate category, but it has long been entrenched on the market between cornflower and royal blue. This color looks very bright under any type and brightness of lighting.
Royal blue is the most expensive variety of blue sapphires. Royal blue is a range of shades of rich, deep blue, but without turning black. The range of this color varies from laboratory to laboratory, so for example the GIT (Gemological Institute of Thailand) has a set of samples of Royal Blue sapphires that also includes darker blue hues. As we mentioned above, such sapphire specimens look dark in Russia, so one should buy sapphires only by seeing the stone in person. Sapphires of this color category are usually used in their collections by Graff-level jewelry houses.
Most of the crystals (90%) go through enrichment to improve their quality characteristics.
The main methods of treating blue sapphires:
Heat treatment is the most common method of treatment. This technology is based on heating the material in a furnace at 900 to 1800 degrees Celsius. The color of a sapphire changes to a more saturated color after heating. In addition to this, it is possible to clarify darker shades of sapphire, altering the coloring and thus increasing the price. The effectiveness of this method is based on the melting of the thin needle-like inclusions of rutile, which sometimes cause an unsuitable color tone. The crystalline mineral inclusions in the stone also melt when exposed to heat and become less visible, thus improving clarity. Of course, refined sapphires differ in price from pristine natural stones.
Titanium diffusion is the high-temperature heating of already cut sapphires with the addition of titanium oxide. Due to the lower atomic weight, titanium diffuses into the surface layers of the stone, making it appear richer in blue or blue. This coloring is easier to diagnose than heat treatment; by putting a diffused sapphire face down on a white sheet of paper, one can see that the coloring is intensified along the edges of the facets.
Filling of cracks with blue cobalt glass: under high temperature and pressure, the glass penetrates the cracks, "healing" them and improving the clarity of the cracked stones.
There are some samples that have been subjected to all three methods of ennoblement at once. Their price is very low and does not exceed $20-40 per carat.
It is also important to keep in mind that at the market there are also synthetic sapphires that are grown at specialized factories. Synthetic sapphires often have a great quality. However, they are quite inexpensive and are supplied to the jewelry market in large quantities. Gemological laboratories verify sapphires and issue documents that certify the true provenance of the stones.
What affects the price of blue sapphires?
The 4C (Color, Clarity, Weight and Cut) principle of diamond pricing only partially applies to the pricing of blue sapphires.
The price of blue sapphires is affected by:
The color of a sapphire is the most important characteristic, it is the color and its saturation that can increase the value of a blue sapphire dramatically. Above we have listed and described the most expensive color varieties of blue corundums: Royal blue, Peacock blue, and Cornflower blue.
The weight of a stone greatly affects its price, especially for natural untreated sapphires. The price per carat increases step by step with the weight of the sapphire in the following weight categories: 1-3 carats / 3-5 carats / 5-7 carats / 8-10 carats and samples over 10 carats. It is important to note that, for example, the price per carat of blue sapphire from category 1-3 carats and category 5-7 carats may differ by two or more times. This rapid increase in value can be seen every one or two categories of weight.
Clarity: Sapphires often have rutile, light needle-like inclusions that give a "silky touch" to the facets of the stone. There are both gas-liquid and hard mineral inclusions that influence the value. When valuing a rare crystal of vivid blue color, the clarity affects the price, but is not the main criterion. Both natural high-grade and synthetic sapphires may have perfect clarity. Therefore, when buying clear stones, you should make sure you have an expert report confirming their natural origin.
Cut - the quality of the cut often affects the value of sapphires. Unlike diamonds, there are no strict parameters for the cut of a colored stone, but symmetry, polishing, and proportions are essential to show the color. The Asian quality of cut is very low, and this is true for both cheap and expensive gemstones. This is due to the chase for more weight in the stone, so the samples are often "stretched" and have deep pavilions. This greatly reduces the "face" of the stone, making it visually smaller than stones of the same weight but with a proportional pavilion. Another sign of a bad cut is the large pavilion, which makes a large window of color failure. Often a sapphire needs to be over-cut to show as much color as possible, so it loses a noticeable portion of its mass.
Treatment. Non-treated samples of blue sapphires are on average 1.5-2 times more expensive than similar in color and size treated sapphires. In this case, we are only talking about heat-treated crystals, since other methods of enrichment (titanium diffusion staining and fracture filling) reduce the cost of a sapphire much more.
Origin - the deposit also affects the cost of blue sapphires. The most expensive sapphires are considered to be specimens from Kashmir (India). But the Kashmiri deposit has long been depleted and closed, and one can rarely come across stones from private collections on the market. Second place goes to sapphires from Burma (Myanmar), where Burmese sapphires of better than 5 carats are very rare. Burmese provenance increases the price of stones as compared to Sri Lankan. It is Sri Lanka that ranks third among the famous sapphire-bearing regions. Nowadays, the majority of blue sapphires of high gem-quality come from Sri Lanka. Sapphires from Madagascar are often as beautiful as Ceylon sapphires, but they cost a little less. Madagascar is a young region compared to the first "brand" three deposits, but experts predict an increase in the price of Madagascar stones in the future. Even now, we do not see much difference in price per carat between stones from Sri Lanka and Madagascar, which are of top quality. In spite of this fact, miners from Madagascar keep bringing rough to Sri Lanka and passing it off as local Sri Lankan rough in pursuit of extra profit.
Certification: The lack of expertise from the world's top gemological laboratories may bring the price of a blue sapphire down, but it is still possible the stone may have a different flaw or origin than the one declared. The most reputable laboratories in the world that can determine not only the origin and the refinement, but also the region of mining: GRS, GIA, Gubelin Gem Lab, SSEF, AGL, Lotus, and AIGS. In Russia, we recommend to check the colored stones at the Moscow Gemological Center of the Moscow State University and MGL, the Moscow Gemological Laboratory.
The cost of blue sapphires
The cost of natural sapphires in beautiful blue shades is growing every year, as is the worldwide demand. It is impossible to give statistics of prices for the top large (8-10 and 10+ carats) blue sapphires in the Royal blue, Cornflower blue, and Peacock blue color categories. The sale of each such precious specimen is a complicated bidding process between the buyer and the dealer; often such deals have a closed format. An average price for Ceylon blue untreated sapphires of the highest gem-quality in the 8-10-carat weight category is defined by the world market as $5,000-8,000 per carat. Unique samples from Burma are much more expensive in the same weight category: $10,000-18,000 per carat. This quality of sapphires is quite a rarity.
Here is the price range for blue sapphires that are more sought after on the market: an average 3 to 5 carats with different gem-quality levels, but never mind the region of extraction:
Low (commercial) quality - in this category are sapphires that have been diffused or heated. The colors are either light or too dark. There are inclusions. Price fork: $50-500/carat.
Good quality - in this group are blue sapphires after heat treatment or without, but light blue in color, the clarity of such stones is usually not flawless. Price fork: $600-1,600/carat.
Very good quality - in this category, blue sapphires are either bright blue in color without enhancement or only warmed, but in top hues. The clarity of such samples is good, but there may be subtle inclusions on the periphery of the stone that are barely visible to the eye. The price range is $1,700-3,500/carat.
Only uncut stones of the most expensive color grades (Royal blue, Cornflower blue and Peacock blue) are of excellent quality, well-cut and visually clear. Price fork: $3,600-$5,000 per carat.
*These prices are averaged, do not take into account annual growth, and are current as of 2017-2018.
Optical effects blue sapphires
Color changing is an optical effect that changes color in different light conditions. In daylight, the stone is blue, but in artificial light it changes to violet.
Asterism is a characteristic feature of starry-cut cabochon sapphires. A star with six rays appears on the smooth surface as the stone shakes. A beautiful star increases the value of a specimen, which is why there are also simulations of this optical effect: the so-called "induced stars. The main feature of such imitations is the absence of displacement of the star when the gem is wobbling.
"Cat's eye" is the movement of a white streak of light across the surface of a cabochon-cut sapphire. The occurrence of these two optical effects is due to the presence of rutile threads throughout the minerals. A certain orientation in the rutile crystal is responsible for the asterism or "cat's eye" effects.
Minerals with optical effects cannot be heat treated, because rutile melts at high temperatures.
Deposits of blue sapphires
The most beautiful jewelry specimens hit the market from:
Lower quality and darker coloring sapphires are mined in: Australia, Thailand, Cambodia, Laos, Vietnam, Tanzania, Nigeria.
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