People sincerely loved to decorate. At first it was ordinary wreaths and necklaces from bright colors, then shells and beautiful minerals. Later, people learned how to process natural, often unbroken crystals so that they became genuine treasures. In this article we will talk about sapphires.
Sapphire is one of the most beautiful and expensive natural gems, and so it was almost always, from ancient times, when a person learned how to produce and handle these natural crystals.
Sapphire, as well as his fellow Ruby, belongs to corundum – mineral, the basis of which is aluminum oxide with various impurities, which are painted crystals in various colors. Distinguish classic and fantasy sapphires. The first group is the crystals of the blue color of a variety of shades. Well, the second belongs to all other corundes, besides saturated-red – these are rubies.
The main parameters for which the color of precious stones are estimated, including sapphires, is a shade, color saturation and lightlot. Standard shade for fantasy sapphires is not in connection with the variety of their colors. And for classic blue crystals, the best is the most better cornflower – the color of sapphires mined in Kashmir.
Physical properties of Corunda
|Compound||Aluminum oxide with various inclusions|
|Moos hardness||9 (second after diamond)|
|Transparency||Varies from opaque to transparent|
|Density, g / cm3||3.95 – 4.0|
|Refractiveness coefficient||1.766 – 1,774|
Sapphires are considered strong talismans. In many sources they write that they help from a bad eye, damage and deception, contribute to the acquisition of wisdom and calm. He loved to wear navigators and travelers, especially they loved asteria stones (star sapphires).
It is also believed that the wearing of Corundum is beneficial on people suffering from insomnia, rheumatism, epilepsy and various infections.
From which the shade depends?
The color of the stone depends on its composition. Even the small presence of extraneous impurities can radically change the colors and purity of sapphire.
The effect of impurities on the color of the mineral
|Titanium and iron salts||Blue, blue, bluish gray|
|Increased content of titanium||Orange|
|Oxide vanadium||Purple or reddish|
|Increased iron content||Sine-green|
|Magnesium, zinc and cobalt salts||Green|
|Chromium, Iron and Titanium Salts||Pink, purple, lilac|
|Hematite (in the form of lamellar crystals)||Brown|
|Almost complete absence of foreign inclusions||Colorless, white|
Color saturation largely depends on the quantity and interest ratio of foreign inclusions. On the simplified scheme, blue sapphires are divided into bright, medium and light stones. Professionals are used when estimating crystals 5 degrees of lightweight and 3 saturation categories.
Main color gamma
Colored sapphires are of the most different colors, excluding, as already mentioned above, saturated red.
The most expensive are the rich-blue gems, followed by the stones of pinkish-orange color (“padparadzha”, which in the translation means “lotus flower”), then pure pink crystals. Yellow transparent sapphires and blue opaque asteria (stones, on the ground surface of which is clearly visible drawing of a 6- or 12-beam star) occupy 4th place in the high cost. The step below is orange, green, purple gems, as well as sapphires with alexandrite effect – that is, changing coloring depending on the lighting. Cheaper than all the colorless stones, as well as black simple and star. In fact, not quite correctly call black sapphires black – they are blue, just because of the high saturation of the color they seem dark and opaque.
Sometimes there are crystals, one part of which is painted in one color, for example, blue, and the second one – in the other, for example, yellow. Such stones are called polychrome, or multicolored, they are quite highly appreciated due to rarity.
How to choose?
When choosing jewelry with any precious or semi-precious stones, require a certificate confirming the natural origin of the mineral. Nowadays, many precious stones grow artificially in autoclaves. The naked eye is impossible to distinguish them from natural. But there is a significant price difference, because natural sapphires are very very and very expensive, and this is already creating ample opportunities for all sorts of fraudsters. Therefore, do not forget about certificates, and in the case of the acquisition of large stones, do not be lazy to order an examination, because it is very easy to deceive.
There is an easy way to check the natural nature of the stone: direct the light of the ultraviolet lamp. Natural crystals at the same time should be greened, and synthetic – no.
When viewing a certificate, pay attention to the assessment of the stone, for example, 1/2. The first figure indicates the color of the stone (1 – blue), and the second – quality category (depending on the purity of the stone and the level of transparency of the crystal). Quality categories total 4. The first includes the stones of the highest purity and transparency, in which there are practically no defects. The second includes transparent sapphires with quality worse – with small defects or with too saturated color. Ophpatic stones of the third category defects can be seen with the naked eye. Well, the fourth group includes turbid crystals with pronounced shortcomings.
Also do not forget to see, there is a stone for refined or not. To improve the quality, most natural sapphires are treated thermally, that is, heated. This allows you to change the color of the stone, increase its transparency and T. NS. On the physical properties of the mineral, this treatment does not affect, but the rough natural sapphires are valued much higher than the processed.
Look through the stone on the light, the best natural. Inside the crystal, microcracks can often be seen, which reduce the quality, and, accordingly, the price of the stone. Rate the cut stone. Sometimes because of the wrong processing or unscrupulous grinding the appearance of the gem seemingly, without reflecting all its possible beauty.
The price of crystals is also highly dependent on the country of their production. The most expensive are the stones mined in Kashmir, on Sri Lanka and in Tanzania. The second go Burmese and Thai crystals. Next – mined in all other countries of the world, except Australia, as Australian sapphires are located on the lower line of the price rating of these minerals. It should be noted that the Kashmir deposit has already been developed and closed. In the Russian Federation there are also several deposits of Corundov – on the Kola Peninsula (blue, greenish, corn lines) and in the Urals (gray-blue).
Also in Russia, as in other countries, artificial corundes produce, because these stones are applied not only in jewelry, as well as in many industries.
About the properties of sapphire is described below.