Sapphire is one of the four precious stones, and the prices of these years have been rising. In high-quality sapphire, words such as Royal blue and Cornflower blue appear at a low frequency. These high-quality sapphires have a certain impact on the value of burning if other quality indicators are the same.
What is "burning" and "no burning"
"Boiled" means that the gemstone is heated, and no burning means that the gemstone is not naturally heated. Heating is to place the gemstone in a device that can control heating, choose different heating temperature and other different conditions for heat treatment, so that the color, transparency and clarity of the gemstone can be improved stably for a long time, thereby improving the aesthetic value of the gemstone and commercial value. For example, after the Sri Lankan sapphire is heated, the color changes from light blue to dark blue.
Why do you want to "heat"?
Sapphire is formed by the slow combination of oxygen and aluminum in the high temperature and high pressure mantle of tens of kilometers underground. Generally, it is mostly corundum. Only a part of the transparency is good, the color is gem-quality, it is called gemstone, and the output is very rare. The high-temperature heating process of sapphire essentially repeats or continues the high temperature and high pressure process in the natural formation, so that the sapphire color, clarity and transparency without proper high temperature formation process are improved and the value is improved.
Sapphire "heating" process
The traditional way is to borax sapphire, then seal the lid, heat it in the furnace with coke, about 5-6 hours, slowly anneal, carefully remove the red simmer with long tongs, put it in aluminum bucket, cover Cover it, break it and take out the sapphire. Some sapphire in the heat treatment process, adding bismuth compounds and other substances, can deepen or change the color of sapphire, even through the elements spread into the interior of the crystal, in the outer layer of sapphire can induce color and starlight.
The commercial significance of sapphire "heating"
Naturally produced red sapphire, the quantity of commercial quality is not much, and the mine source is almost exhausted. If the natural process is repeated without heating, the sapphire on the market will shrink sharply.
In addition, the heating of the sapphire is very stable, and its color does not change in the everyday wearing environment. Most sapphire in the global jewellery market is optimized for heating, and “heating†is also an optimized method accepted and recognized by international gemological laboratories.
How to judge whether there is burning or burning
1. The color tone of the gemstone changes, for example, it is originally light yellow or pink, burned into dark yellow, dark brown, yellow, golden yellow; some milky, silky gray rough (geuda) burnt blue; dark blue shallow Blue can also be burnt to pure blue.
2. After the high temperature heat treatment, the contents of the gemstone may undergo a series of changes, such as the needle-like inclusions become intermittent, the gas-liquid inclusions burst, the low-melting inclusions are rounded, the filamentous rutile needles disappear, etc.
3. For gems with more titanium, you can burn star red and sapphire.
4. For sapphire to which a substance such as a ruthenium compound is added, it can be detected by a component test.
The certificate of the domestic testing organization does not indicate the sapphire “burning without burningâ€, such as NGTC (National Jewelry Quality Testing Center) and GIC (China University of Geosciences Jewelry Testing Center). Only the GUBELIN and GRS in Switzerland, the AGL in the United States, the GIA in the United States, and the EGL in Sri Lanka have the identification mark for "burning without burning".
If the stone is heat treated or the color is not natural, then the letters H, E, LIBS, etc. will be displayed in the comment item:
A represents no indication of thermal treatment.
E (Enhanced) represents an optimized treatment, including optimization of clarity and/or color after heating, and the healing of cracks and holes may contain traces of foreign residues, which are regarded as permanent treatment.
H is commonly known as "old burning" or "old burning"
H (Heated) represents no residue in the heat treatment and is regarded as a permanent treatment, which is only subjected to a simple heat treatment without being colored.
If it is marked below, it means that the gemstone has been artificially processed and has no value. It will be marked in the domestic certificate: sapphire (handling).
H(a)/(b)/(c)/(d) is commonly known as “new burntâ€
H (a) heat treatment of trace residues (healing cracks and residues such as borax) in a small range of color injection, the properties are relatively stable.
H (b) heat treatment of a small amount of residue (healing cracks and residues such as borax), a large amount of internal coloring, the nature is not stable.
H(c) represents all the color injections in the heat-treated medium amount residue (residues such as borax or glassy material in the crack or hole healing area), and the properties are extremely unstable.
H(d) represents a significant residue of heat treatment (residues such as borax or glassy material in the crack or hole healing).
H(Be) represents a heat treatment with a slight element and a helium diffusion treatment.
E(IM) represents a diffusion heat treatment consisting of a slight element such as yttrium element, which induces the formation of color gamut and color center (this method is different from traditional surface thermal diffusion treatment), which is regarded as permanent treatment, and special attention should be paid to color area re-cutting. unit.
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