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Sapphire purity classification


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Sapphire is considered a gem, the second after a diamond in value, beauty and hardness. When buying sapphire, you should know how to evaluate the quality of the stone in order to be sure that you will get the maximum for your money. You also need to wisely approach the buying process, know where and how to buy, so that you are not asked to get too high a price.

Key quality parameters

The rule of four "C" for determining the value of sapphire is based on the most important characteristics of the stone, the name of which in English sound begins with this letter:

In Russian, these words consistently mean color, purity, cut and weight (karate). The first two parameters are determined by the jeweler visually, that is, by eye. A magnifier is used to increase visibility. Tenfold amplification is enough for an experienced gemologist to discern possible defects in the stone.

The main physical characteristics of sapphire include glass luster, a hardness value of 9 units (Mohs), and the absence of cleavage in crystals. The last indicator affects the appearance of the fracture. On the surface formed when the mineral is split, a shape similar to a bivalve mollusk shell is clearly visible.

Grades of purity

Transparent and opaque sapphires are found in nature. The former are estimated to be more expensive, because the appearance depends on how the rays of light pass through the crystal (especially after cutting). A stone through which light rays do not pass is much lower than a stone in which the sun plays in the reflected faces.

The beauty of the playing rays will be the more beautiful, the purer the sapphire. The purity of the stone is rated in four categories. The first includes perfectly transparent minerals. Microscopic inclusions are permissible, which are noticeable with a multiple increase of hundreds of times.

The second group consists of sapphires with larger inclusions. However, they also should not be visible to the naked eye. Minerals with bubbles and defects noticeable without devices belong to the third category. Often these stones are cloudy.

The classification also includes a group of opaque gems. This is the fourth category of sapphires for which serious defects are permissible. And although such minerals are not classified as jewelry, jewelry from them is in demand, due to the low price. In this case, the cut is usually done in cabochon.

Mysteries of the color palette

The color of sapphire is another major indicator when evaluating a jewel. The most popular classical tone is velvet cornflower blue, that is, saturated bright blue. Fantasy shades are found in nature - pink, orange, green, yellow. Red stones are not included in this group; they are called rubies. But here they include the famous pink-orange padparajas - lotus-colored sapphires. For details, see the article “Properties of sapphire stone and to whom it suits.”

There are jewelry sapphires that are able to change color under different lighting conditions (pleochroism). When processing some stones with a cabochon in the center, a six-pointed star is observed, which indicates the effect of asterism. A star with 12 rays is less common.

The classification of shades distinguishes two blue species - royal and cornflower blue. Their prices depend on the place of sale. In sapphires, royal sapphires are more expensive, and in Russia they do not spare money for cornflowers.

The answer to these differences lies in the sun. In the northern latitudes, where it is not enough, the first color variety looks too dark. A lighter cornflower blue color (cornflover blue) looks advantageous. In the rays of the southern sun, it is royal sapphires (royal blue) that show a deep and rich color.

Cutting matters

Rule of the Four “Cs” focuses on sapphire cutting. High-quality processing allows you to show in the best possible way the extraordinary radiance of the stone. The cost of the gem directly depends on this beauty.

In processing the following matters:

  • proportions
  • symmetry,
  • lack of damage (chips, scratches, pits).

An experienced jeweler observes the first two important parameters, and conceals possible defects in the pavilion (the lower part of the faceted stone) or under the rim of the item.

Over hundreds of years, a certain selection of cuts has been established. Pear, marquise, oval, “heart” or “emerald” are suitable for large sapphire. The round shape is most often chosen for small stones.

As mentioned above, sapphire with asterism is cut in cabochon and polished to achieve the desired effect.

We look at the tag

An obvious indicator for setting the price of sapphire is the size of the stone. Weight is determined in carats. This unit of measurement is accepted for all precious minerals and is equivalent to 0.2 g.

Blue corundums weighing more than 5 carats are rarely found in nature. And if you are offered a huge stone in the guise of a precious one, then that means there is reason to think about its naturalness. And to begin with, you should look at the tag that accompanies the product. This tiny little piece of paper contains a lot of useful information.

The first figure immediately indicates the number of stones in the jewelry. The designation "C" or "Sapph." Indicates the name of the jewelry. The following hint relates to the type of cut. If it is a pear, then we will see the abbreviated "Gr.". Oval is marked as "Ov.", And the marquise is marked with the letter "M". The next figure is not always in the designation, but if there is 53 next to the “Cr.” Sign, this indicates a round shape and facet cut on 53 faces.

In sapphire cuts, the shape of a square is also used, sometimes a rectangle and even a triangle. However, during processing, the corners are rounded so that there are no sharp transitions.

Color and purity designations

The numbers, which are separated by an asterisk, indicate the size of the stone. And the next value indicates the weight of sapphire in carats. The listed data looks like this: “1Sapp. M 6 * 4 0.58 2/2 ".

It remains to explain the indicators of sapphire - 2/2. So indicate the color and purity of the mineral. In this example, the number “2” means that the stone is medium blue in saturation. For the lighter, the designation “1” is accepted, and “3” will indicate the completely dark ones.

The number "2" after the fraction indicates that there are inclusions in the gem, visible under a tenfold magnifying glass. If they are visible with the naked eye, then put “3”. In the case of inclusions that are distinguishable only with a multiple increase, “1” is put in the notation. Thus, the sapphire marking 3/3 says that the stone is dark blue and not clean enough.

Foreign signs

If sapphire is processed abroad, then marking the purity of the stone on the tag will look different. For example, the smallest inclusions that are not visible to the ordinary eye are indicated by VVS. Slightly larger - VS.

Small bubbles and rutile needles visible without instruments are indicated by the letters SI, and inclusions are clearly visible by the same letter I. There is an innovation of American gemologists for absolutely transparent sapphires - IF. However, in nature such stones do not exist. A similar sign on the label indicates the artificial origin of the stone. The article “The Difference between Synthetic Artificial Sapphires and Natural Sapphires” deals with just that.

The concept of quality sapphire includes all of the above indicators in aggregate. A stone with categories 1/1 speaks of extreme purity, deep blue color and is valued above others. But in the future, the cost already depends on the size and quality of the cut.

To correctly evaluate the characteristics of sapphire, it is advisable to use a magnifying glass when buying. It is difficult to determine the advantages and disadvantages by eye.

Carat Details

As indicated above, the mass of sapphire is calculated in carats. When buying jewelry, it is difficult to determine the exact weight of the stone. After all, pulling the mineral out of the weighing frame will not work. In this case, a table of correspondence of size and mass for different forms of cut will help.

To select, use a standard measuring ruler with a graduation in millimeters or a vernier caliper. If you do not find a difference between the two sapphires of the same size, except for the price, ask about the origin of the jewelry. The place of production is another indicator of quality.

Origin affects price

Blue and fantasy corundums are found all over the world - in Australia, USA, Vietnam, China. But each mine has its own specific features of crystal nucleation. Consequently, the quality of the jewelry is different. The sapphires that are mined in Ceylon, in Tanzania and in the Indian province of Kashmir are considered the cleanest.

Corundums of Southeast Asia (Thailand, Myanmar) are not much worse. This region is also famous for its high quality. But sapphires from Australia are significantly inferior in price, like those that are found in Russia. The Ural Mountains - a source of sapphires with a grayish tint, the Kola Peninsula gives crystals of cornflower blue color.

Heat cleaning

There is the concept of ennobled sapphires. Special treatments were applied to them to improve quality. The thermal method is widespread, giving a saturated color to a faded crystal. By the action of temperatures, some inclusions disappear, making the jewel cleaner. It is believed that 90% of the minerals undergo refinement. So the opportunity to purchase a purely natural stone is negligible (1 out of 10).

We talked about how to choose sapphire yourself. But having no experience in determining the quality of precious stones, try to buy jewelry in trusted retail outlets. In such jewelry stores, you can require a certificate of conformity and a license to trade.

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The cost of navy sapphire

Blue sapphire is the most expensive kind of mineral. Its color is so deep that if the stone is clean, it is even difficult to determine the saturation of the blue color by eye. The price of dark blue sapphire varies from $ 300-1000 for 1 carat. More expensive will be those that did not initially undergo additional heat treatment to improve cleanliness. The standard of blue sapphire is considered to be Kashmir, in which the structure of the mineral is most pronounced.

The cost of sapphire yellow shades

To determine the value of sapphire with an admixture of yellow shades, the color of the stone is important, and, of course, its faceting, which emphasizes the radiance and shade. To stones of a lower category than blue sapphires include:

  • "Padparaja" - a stone of orange, pink or purple hue. Stones of this grade weighing more than 5 carats are not used in the jewelry industry and are considered collectible. Their price can reach from $ 30,000 per 1 carat. The price per carat of jewelry "Padparaja" varies between 130-150 $ per carat,
  • saturated yellow or golden stones will cost $ 100-130 per carat,
  • green sapphires also exist. Their complex heterogeneous color is achieved through a combination of yellow and blue veins. These corundums are not so expensive and can cost from $ 75 per carat.

The cost of white sapphire

The white color and transparency of the mineral structure indicate the complete absence of extraneous impurities, for natural minerals this is an extremely rare occurrence.

Transparent sapphire resembles a diamond; in jewelry, you can often find combinations of these stones. Given that colorless corundum is not common in nature, white color is usually obtained by heat treatment and the procedure for bleaching colored stones. Such a sapphire will be inexpensive.

Natural Mineral Colors

The most popular sapphire crystals are usually blue, ranging from deep blue to light purple. Although experts say that the cornflower blue is the perfect shade for the blue gem.

However, the number of color variations of this mineral is much wider. They are yellow, pink green, colorless, orange and brown. The only color that sapphire cannot be is red. Since the stone of this shade will already be a ruby.

If we are talking about the most popular variety - blue, then the color of a good mineral should be of medium intensity. Not so dark that it can be confused with another color, and not so light that sapphire can be mistaken for another lighter stone.

Almost all sapphires on sale go through the process of “ennoblement”. Most often, it consists in a strong heating of the crystal to 2000 degrees so that it acquires a more uniform and saturated color. This method is also good because only very high quality specimens can withstand such processing. There are also chemical methods to refine sapphires, but they are reversible. Those. after the crystal is polished again, its color will change. Information on what methods of additional processing the stone was subjected to must be announced to the client of the jewelry store before buying.

Upon receipt of synthetic sapphires, their color occurs due to oxides of titanium and iron, but finding the ideal proportion of these components is not easy. Therefore, artificial gems may have an uneven "striped" color. Of course, they can also be subjected to heat treatment to obtain a good color, but synthetic sapphires have another distinguishing feature. Most of these crystals in ultraviolet light have a greenish tint, while natural stone glistens in white.

Star sapphires are of particular value. These are cat-eye minerals.. But only instead of one light band, they have a light pattern consisting of six intersecting rays. They are cut only in the shape of cabochons. To distinguish such a gem from imitation is very simple: rotate the jewelry. In natural sapphire, the "star" will move at the same time. And at a fake it will always be located in the center of the cabochon.

A bit of history

Scientists succeeded in synthesizing sapphire at the beginning of the 20th century. And in the 60-80s. a large number of gold jewelry with these artificial stones went on sale in the USSR. Buyers were rarely informed that they were not buying a natural gem. So if you are offered, for example, a sapphire ring from this time period, then the likelihood that the insert in it will be artificial is very high.

Identification of inclusions

Natural sapphire must contain inclusions. But they should not be visible with the naked eye. Although this is not proof that the gem was obtained in laboratory conditions, it is an obvious fact that the crystal in front of you is of very poor quality.

It is best to consider stone inclusions with a magnifying glass. Although jewelers do this by immersing the crystal in a transparent container with monobromonaphthalene, which is placed on a white sheet of paper. But maybe just a can of water may come up. The difference between artificial sapphire and natural will be that in natural stones all inclusions will be straight stripes. Whereas synthetic ones have curved ones.

Caution: Doublets

Bonding minerals of different quality or natural sapphire and counterfeit is not common, but still such a method of imitating a more expensive stone is quite possible.If the gem rim hides its bottom, then it is very, very difficult to recognize a doublet. However, an ultraviolet lamp can come to the rescue here. After all, even if different parts of the stone will not glow differently or will not glow at all, the glue that connects them will certainly begin to fluoresce.
Sapphire is the second hardest mineral after diamond. Therefore, its edges should be perfectly even. If you notice any chips or irregularities - hardly a real sapphire in front of you.

Origin and documents

Sapphire stone is quite expensive. Therefore, as a rule, any jewelry with a similar gem should have a certificate in which information about the mineral deposit, its weight, etc. will be indicated.

Sapphires are mined in India, Burma, Sri Lanka, Thailand, Vietnam, Australia, Brazil and Africa.

Indian (especially Kashmiri) and Burmese gems are one of the most expensive. And extremely rare in recent years on sale. Therefore, if you are offered such a stone for a couple of hundred dollars - this is a serious reason to think about its authenticity.

Often, instead of laboratory-grown stones, other natural or synthetic crystals of blue color are given out for sapphires. In this case, you can determine what kind of crystal is in front of you using a refractometer. The light refractive index for sapphire will be from 1.762 to 1.778.

In any case, if you doubt the authenticity of the mineral that you are offered, it is best to seek help from a gemologist. Since only a professional is able to determine the quality of a gem with maximum accuracy.

Cost star sapphire

Star-type sapphires got their name due to the effect of asterism on the surface. From a large amount of impurities, accumulations of titanium oxides are formed inside the stone, resembling needles in shape, and on the surface of the stone the reflection of light takes the form of a six-pointed star. Stones with a star structure are designed in the form of cabochons to maintain an unusual effect. The color of star sapphire can be orange, golden or black, while the price is low, about 10-15 $ per 1 carat.

Sapphire cost per carat in Russia. What else affects the price

Prices for carats of sapphire in Russia do not differ from world prices, they are usually indicated in dollars and may vary depending on the price jumps.

In addition to color, the price per carat of sapphire is affected by:

  • The weight of the stone. The cost of a carat of a gem increases with its weight. So the price per carat of “heavy” sapphire, whose weight reaches 10 carats, can increase up to $ 10,000.
  • The purity of the stone. The price of sapphire is affected by the quality of its structure, the presence of turbidity, impurities. Pure sapphires without inclusions can cost from $ 6500 to $ 9500, while the price of the lowest quality sapphires will be in the range of $ 50-500.
  • The quality of the cut. If the quality of the initial stone is not high, then domed stones or carved sapphires are produced from corundum. The price of such a sapphire is about $ 10-20, but not per carat, but apiece.
  • The origin of the mineral. Burmese sapphires are one of the most expensive, and the cheapest corundums are grown in laboratories. In the world there are many laboratories for the synthesis of precious stones, mainly for industry, less often - for jewelry. Although now many designers prefer inexpensive synthetic corundums of different colors - from blue to yellow.

How to distinguish natural from artificial sapphire?

There is nothing wrong with artificial stones, they are environmentally friendly, and in quality they are no worse than natural ones. But what if you want to buy a natural stone and you have doubts? If you buy a jewelry with sapphire, it seems to you too cheap, and the crystals are too transparent, most likely in front of you are artificial or ennobled stones. When buying jewelry, always require a certificate, so you can distinguish natural stone from artificial stone, and artificial stone from beautifully faceted glass.