Natural sapphire refers to a variety of the mineral corundum, different blue hues. The stones having a color different from blue, and blue, belong to the category of fancy sapphires, for example yellow, pink, purple, padparadscha, green or colorless. The cost of sapphires blue hues strongly increases with increasing mass of the stone. This circumstance is due to the fact that the crystals of large size is produced very rarely.
Color palette transparent blue sapphires varies widely. Distinguish the presence of blue and blue tones of different intensity. There are instances of blue-violet or blue-green shades, but the most valuable and rare stones include samples uniform bright blue color.
The most rare and expensive color varieties of blue natural sapphires are:
(Cornflower Blue) cornflower - crystals "cornflower blue" tones are characterized by a "silky" effect of the weak inner glow. These properties are associated with the presence of inclusions of rutile, that reflect light rays. The benchmark is the blue flower of cornflower, but sapphire is a whole range of colors from bright blue to bright blue, but not dark. It is important to note that for the Russian market the stones of cornflower blue velvet-blue color fit more than the Royal blue. The reason is a large number of cloudy days, resulting sapphire "royal blue" in our band can look dark and lose its charm, unlike Asia, where they look very expensive and aristocratico.
(Peacock blue) color, a bright blue peacock neck or the feathers on its tail - this bright blue found in sapphires from Sri Lanka, another name for this bold colour "electric blue". Not all labs make this color in a separate category, but in the market it is long-established between cornflower and Royal blue. This color looks very bright in any type and brightness of lighting.
(Royal Blue) Royal blue is the most expensive variety of blue sapphires. Royal blue is a range of hues for a rich, deep blue color, but not rolling in the black. The boundaries of this color range in various laboratories world are different, for example, in GIT (Gemmological Institute of Thailand) set of samples includes sapphires Royal blue and dark blue shades. As we already wrote above, in Russia such samples sapphires look dark, so buy the sapphires should be only seeing the stone in person. Sapphires of this color category are typically use in their collections jewelry house Graff level.
Elevation blue and light blue sapphires
A large part of the crystals (90%) goes through refining, improving quality characteristics. The main methods of refining blue sapphires:
Heat treatment is the most common method of treatment. The technology is based on prolonged heating of raw materials in a furnace at a temperature of 900-1800 degrees. After heating, a change in the color gamut for more saturated. In addition, you can lighten the sapphires are dark shades, change color, and thereby raising the price. The effectiveness of the method based on melting a thin needle-like rutile inclusions that cause sometimes the wrong color tone. The same crystalline mineral inclusions in the stone under the influence of high temperature melt and just become less visible, improving the purity. Of course, refined sapphires vary in price from intact natural stones.
Titanium diffusion is a high temperature heat already cut sapphires with the addition of titanium oxide. Due to the smaller atomic mass of titanium penetrates into the surface layers of the stone, staining it a darker blue or blue. To diagnose this refinement is easier than heat treatment, marking sapphire diffusion area down on a white sheet of paper, one can observe the increasing concentration of coloring in the edges of the faces.
Filling cracks blue cobalt glass under high temperature and pressure, the glass penetrates the cracks "heal" them and improving the purity of fractured rocks.
There are samples that were exposed at once to all three methods of treatment. Their cost is very low and does not exceed $20-40 per carat.
It is also important to remember that there are artificial sapphires that are grown in specialized industries. Synthetic sapphires often have excellent quality characteristics. However, they have a very low cost and are available in the jewelry market in large quantity. Gemological laboratory test sapphires and issue documents attesting to the true origin of the stones.
What affects the cost of blue sapphires?
The principle of formation of the cost of diamonds "4C" (Color, clarity, Weight and Cut) is only partially applicable to the pricing blue sapphires. On the value of blue sapphires is affected by:
The color of the sapphire is the most important feature, namely the color and its saturation can increase the value of the blue sapphire dramatic. Above we have listed and described the most expensive color varieties of corundum blue: Royal blue, Peacock blue, and Cornflower blue.
Weight - the weight of the stone affects the value, especially for natural untreated sapphires. The cost per carat speed increases with increasing mass of sapphire in the following weight categories: CT 1-3 /3-5 carat /Karat 5-7 /8-10 carats and specimens over 10 carats. It is important to note that, for example, price per carat blue sapphire from the category of 1-3 carats and categories 5-7 carat can vary in two and more times. Such a rapid increase in the cost, you can observe every one or two categories of weight.
Purity sapphires are often bright rutile needle inclusions that gives a distinctive silkiness to the faces of the stones. Meet the gas-liquid and solid mineral inclusions, which have an impact on the cost. When assessing rare crystal bright blue, the purity of the mineral affects the price, but not as the main criterion. Perfect transparency can have a high-quality natural stones and artificial sapphires. Therefore, when buying pure stones, you need to ensure the availability of expert opinion, confirmation of natural origin.
The cut quality of the cut often affects the value of sapphire. Unlike diamonds to colored stones, there is no strict cut parameters, but the symmetry, Polish and proportion are of great importance to demonstrate the color. Asian cut grade is very low and this applies to both cheap and expensive stones. This is due to the pursuit of a greater mass of stone at the output, so the samples are often "drawn" - with deep pavilions, which greatly reduces the "face" of the stone, making it visually smaller than the stones with the same weight, but proportional to the pavilion. Another sign of a bad cut - a large area where there is a large window with the failure color. Often for maximum color demonstration of the sapphire recut is required, in which there is a loss of a tangible part of its mass.
Elevation - untreated samples blue sapphires are on average 1.5-2 times more expensive than similar in color and size sapphires ennobled. In this case we are only talking about heat treated crystals, as other methods of upgrading (paint, titanium diffusion and fracture filling) reduce the cost of sapphire is much stronger.
The origin - field also affects the value of blue sapphires. The most expensive sapphires are considered the instances from Kashmir (India). But the Kashmir field long ago, and closed, on the market rarely seen gems from private collections. The second place is occupied sapphires from Burma (Myanmar), the Burmese high quality sapphires over 5 carat are very rare. Burmese origin significantly increases the cost of the stones compared to the Lankan. That is Sri Lanka ranks third among those of the eminent sapphirerose regions. Today, most blue sapphires of high quality jewelry marketed from Sri Lanka. Sapphires from Madagascar are often not inferior in beauty of Ceylon, but the cost on them below. Madagascar is a young region compared with the first "branded" with three fields, but experts predict the rising cost in the future on samples from Madagascar. Now for the top quality stones from Sri Lanka and Madagascar, we see no significant difference in the cost per carat. Despite this, the miners from Madagascar continue to bring raw materials to Sri Lanka and to give his local Sri Lankan, in pursuit of extra profit.
Certification - absence of expert opinion leading Gemological laboratories may slightly reduce the cost of sapphire blue, but it also poses the risk that the stone may be heated or be different from the stated origin. World's most prestigious laboratories that can determine not only a natural origin and refinement, but the region of production: GRS, GIA, Gubelin Gem Lab, and SSEF, AGL, Lotus, AIGS. In Russia we recommend you to check the colored stones in Moscow Gemological center of Moscow state University and the IPF - Moscow Gemological laboratory.
The cost of blue sapphires
The cost of natural sapphires are a beautiful blue hues growing every year, and growing global demand. Statistics of the prices for the top large (8-10 and 10+ carat) blue sapphire color categories Royal blue, Cornflower blue and Peacock blue impossible. Selling each precious sample is a complex bidding process between buyer and dealer, often such transactions are of a proprietary format. The average prices for blue untreated Ceylon sapphire of the highest quality jewelry in the weight class of 8-10 Karat world market defines as - of $5,000-8,000 per carat. Unique specimens from Burma in the same weight category significantly more expensive - $10.000-18.000 per carat. Similar quality sapphires are rare.
Give a price range on more marketable features blue sapphires is the average weight of 3-5 carat with different levels of quality jewelry, but excluding the mining area:
Low (commercial) quality - in this category sapphires, which were subjected to a diffusion or heat. Colors, or bright, or too dark. There is inclusion. Fork price: $50-500/CT.
Good quality in this group blue sapphires after heat treatment or without, but light blue colors, the purity of these stones are usually not perfect. Fork price: $600-1.600/carat.
Very good quality - in this category blue sapphires are a vivid blue color without any treatment, or only heated, but top shades. The purity of such samples is good, but can be barely visible to the eye inclusions located on the periphery of the stone. Fork price: $1.700-3500/CT.
Excellent quality - only untreated stones are the most expensive color varieties (Royal blue, Cornflower blue and Peacock blue) with a good cut and visually clean. Fork price: $3.600-5.000 US $ per carat.
*Listed prices are average, do not account for annual growth and actual for the 2017-2018 year.
Optical effects blue sapphires
The color change is an optical effect, which changes color in different light. At daylight the stone has a blue tone, but in artificial light it changes to purple.
Asterism - this optical effect is common for star sapphires in the cabochon gemstone. On a smooth surface there is a star with six rays, sliding across the surface, with rocking stone. Beautiful star increases the cost of the sample, therefore, meet you simulate this optical effect, the so-called "induced" stars that are artificially applied to the surface of the stone. The distinguishing feature of imitation is the absence of displacement of the star with rocking gem.
Cat-eye - move the white light strip on the surface of the sapphire cut in cabochon. The occurrence of these two optical effects is due to the presence in the minerals rutile threads throughout. A certain orientation of the crystal of the rutile responsible for the manifestations of asterism or "cat's eyes".
Minerals with optical effects cannot be subjected to heat treatment, since rutile is melted at high temperature.
Deposits of blue sapphires
The most beautiful jewelry specimens are put on the market of: