Friends who often read our popular science know that there are many ways to optimize the treatment of gemstones: dyeing, heat treatment, irradiation, filling, diffusion and so on.
But to say that in the gemstone is more common, the most traditional and the most "unconscious" optimization treatment method, should be heat treatment, buy red sapphire friends will be particularly familiar with this word, is often said "burned / no burn".
<h1 class="pgc-h-arrow-right" data-track="66" > heat treatment is not "treatment"? People are "optimizing"! </h1>
First of all, we need to know that the optimization and treatment of gemstones are two concepts, optimization (Enhancing) is equivalent to makeup, treatment (Treating) is equivalent to plastic surgery.
The Enhancement of gemstones in Systematic Gemology is defined as all methods used to improve the appearance (color, clarity, or special optical effects), durability, or usability of gemstones, except for cutting and polishing.
Fluorescent brightener optimized pearl, source jeweler
Optimization refers to "the traditional, widely accepted ways to improve the potential beauty of jewelry and jade", which is acceptable to everyone, unless there is a certain degree of impact on value, otherwise many times the merchant will not specifically state.
Such as heat-treated rubies, dipped in colorless oil emeralds and chalcedony, agate dyeing, etc.
Art Déco style platinum pendant necklace, by Georges Fouquet, 1925.
SSEF certified emeralds are from Colombia and are micro-oil treated.
Treatment refers to "unconventional and not yet accepted methods of improvement", which is less accepted by everyone, and the value of treated gemstones will be greatly reduced.
Such as dyeing treatment of jadeite, irradiation treatment of blue diamonds, surface diffusion treatment of sapphires, glass filling treatment of rubies and so on.
Filled ruby stud earrings, source network
For gemstones that have been "treated", the national standard stipulates that when issuing an appraisal report, it must be accompanied by an explanation.
In most cases, the "optimized" gemstone does not need to be noted (in some cases, it is necessary to note the explanation, such as: the national standard "Jewelry and Jade Name GB/T 16552-2017" stipulates that the surface of natural organic gemstones is optimized and should be noted).
Graph source network
In the international industry, the heat treatment of gemstones is highly accepted, and it is usually optimized by default.
<h1 class="pgc-h-arrow-right" data-track="364" > burned? How is it burned? </h1>
Heat treatment, commonly known as "burning", is to use artificial equipment to imitate the temperature of the natural geological environment, artificially control the heating temperature and heating time and other external conditions, and quickly change the appearance of the gemstone in a short period of time, which can be seen as the artificial repetition and continuation of the natural geological process.
Small Class:
The principle of heat treatment of gemstone: change the content and valence of pigment ions under high temperature conditions, adjust the internal structure of the crystal to eliminate internal defects such as some inclusions, and change the color and transparency of the gemstone.
Heat treatment is a purely physical optimization method that does not change the chemical properties of the gemstone, and is generally accepted in the industry.
"Red jade" after heat treatment
The gemstone is placed in a device that can control heating, and different heating temperatures and other different conditions (redox environment) are selected for heat treatment, so that the appearance characteristics such as color, transparency and clarity of the gemstone are improved for a long time, thereby improving the aesthetic value and commodity value of the gemstone. - Gemology Tutorial
Sapphire before and after heat treatment, source network
Most people think that heat treatment simply changes the color of a gemstone.
However, in fact, proper heat treatment will also remove noise to improve gem color, crystal melting to produce gemstone starlight, eliminate mercerization to improve gem clarity, clarify the interior to enhance gem transparency, restore defective crystal structure to improve gem color, dehydration to improve gem color, etc.
Before and after ruby heat treatment, source network
<h1 class="pgc-h-arrow-right" data-track="317" > heat treatment of common gemstones</h1>
corundum
There is a burning / no burning is a concept that will inevitably be mentioned when buying larger particles of natural red and sapphires, and if there is a small stone, there is generally no one to burn without burning, anyway, the price is almost the same.
The heated ruby is still natural, equivalent to a small micro-shape, stable and beautiful in nature.
At present, 90-95% of corundum gemstones (red and sapphire) on the international market are heat treated by different methods.
Image source GIA
In terms of price, if it is the same ruby with poor color clarity or average appearance, the price after burning will be higher than before burning.
But if two rubies of similar quality, one is "non-burned" and one is "burned", then the price of the unburned one is much higher than that of the burned one.
This is the reason why things are scarce and expensive, and natural beauties are more scarce than cosmetic beauties.
Generally, when the international authoritative gem identification agency issues a report to the red and sapphires, it will be marked with or without burning.
Tanzanite
In addition to the red sapphire, the small partners who often read our articles should also know that tanzanite is mostly heat treated.
Tanzanite rough
Tanzanite has an interesting feature, it has a strong trichroptry. In addition to blue-purple, natural Tanzanite is often green-blue with brown tones, as well as gray, brown, yellow, green, light pink and so on.
Tanzanite rough in different colors
Most tanzanite on the market today is heat treated to remove brownish green, yellow-green, gray-yellow, brownish-yellow tones, and deepen the blue and violet hues.
Hortus Deliciarum Tanzanite Gold Ring, by Gucci
Topaz
Most of the Brazilian pink and red topaz on the market is the product of the property's yellow and orange topaz heat treatment.
However, natural pink-red topaz is also produced, but it is very rare.
Brazilian two-color topaz
However, it is reported that not all yellow topaz can be heat treated to turn red, and only yellow- orange-yellow topaz due to the color of chromium can obtain pink topaz after heat treatment.
The temperature of this heat treatment is not high, and it is said that it can be done with an alcohol lamp.
Heat treated pink topaz, source network
aquamarine
Many natural blue aquamarines, without any treatment, will have a little yellow-green hue in their color, and there are very few pure blues.
Therefore, many blue aquamarines are almost all heated to remove the green hue.
Xinjiang's unheated rough aquamarine, the color is light blue-green, source: back to Sri Lanka
After heating (usually between 250 and 700 degrees Celsius), the yellow-green hue inside the gem is removed, resulting in a thicker blue color of the gem.
A rough aquamarine, heat-treated on the left half and primary color on the right, Source: Back to Sri Lanka
Tourmaline
Tourmalines that are darker in color (such as dark blue, dark green, dark yellow-green, dark purple red, etc.) are sometimes heated to make them lighter in color, thereby enhancing their transparency and improving their gemstone grade.
However, because the overall price of tourmalines of ordinary colors is not high, heat treatment is rare. As the "carry handle" variety of tourmaline family, the upstart "Paraíba" is the hardest hit area of tourmaline heat treatment.
Paraíba Sugar Tower Ring, by Theo Fennell
In the previous article we introduced: in the naming, the color is blue (neon blue or purple), blue-green blue, or green, containing copper and manganese elements of tourmaline, can be called "Paraíba" tourmaline, regardless of the origin.
Non-burning Mozambican Paraíba, photo by Robert Weldon
But in the market, you can rarely see the purple Paraíba tourmaline.
Because for commercial value, most of the purple paraíba becomes expensive neon blue paraíba by heating.
Before and after heat treatment of Paraíba, Mozambique, photo by J.C.Zwaan
zircon
Heat treatment can change the color of natural zircon, but also can change the type of zircon.
Colorless, blue, yellow and orange-red zircon can be obtained by heat treatment, and zircon from different origins will appear different colors after heat treatment.
Vietnamese zircon, source network from N. T.M. Thuyet
Heat treatment under reduced conditions can produce sky blue or colorless misalignment.
The most important of these is the Vietnamese reddish-brown zircon raw material, which is heat treated to produce colorless, blue and golden yellow, which is the most common variety of gemstone jewelry.
Heat treatment under oxidation conditions produces golden and colorless zircon at temperatures up to 900C, and some samples can be red.
- Systematic Gemology
However, it should be noted that some heat-treated zircons are exposed to strong sunlight or will partially or even completely return to their original color over time.
Heat treated Vietnamese zircon, source network, from L. T. T. Huong
crystal
As we mentioned in the previous article, the heat treatment of crystals is mostly used for some less colored amethysts.
Poorly colored amethysts can be heated to produce intensely colored citrine or produce transitional varieties of green crystal.
<h1 class="pgc-h-arrow-right" data-track="34" > heat treatment of common jade</h1>
agate
There are excellent varieties of natural red agate, such as southern red, warring states red, and non-red, which are famous for their red. However, the vast majority of brightly colored ordinary red agate on the market is heat treated or dyed.
Uneven light brown agate is heated directly in the air and can become a more uniform, brighter red agate.
Principle: When agate contains a small amount of limonite. Under high-temperature oxidation conditions, fext in limonite is converted to Fe*, and the moisture is eliminated, and limonite is converted to hematite, thus turning agate into a more vivid red color.
Tiger Eye Stone
Many people have the impression that the color of tiger eye stone is natural, but in fact, some brownish red and gray-white tiger eye stone colors are also heat treated.
The heat treatment principle of Tiger Eye Stone is the same as that of agate. Under oxidation conditions, the yellow-brown tiger eye stone can be transformed into brownish red by heat treatment.
Tiger eye stone can be converted into grayish yellow and off-white under reducing conditions, and has previously been used in the market to imitate golden emerald cat's eye.
jadeite
The heat treatment of jadeite is mostly used on the dull color of "jade", the purpose is to promote the occurrence of oxidation, so that yellow, brown, brown jadeite into a bright red "red jade".
The heat-treated "red jade" has the same durability as the natural red jadeite, and because it is optimized by the "physical method" to make it more beautiful, the identification can be compared with the natural jadeite that has not been optimized, and the "A goods" certificate can be issued. It's just that visually, the burned emerald color is more rigid and dull.
(Related reading: The jadeite you bought turned out to be "braised"? But the certificate says it's A goods)
Wada tama
In the case of the discolored imitation seed material and the "two epithelium" of the seed material, most of the bright fake skin is obtained by dyeing.
"Burning color" heat treatment is a relatively advanced and mysterious means, can make the skin color more colorful Hetian jade in the market is a small part, usually only in the true and false high-quality Hetian jade imitation seeds appear, in.
"Two upper" and Tian Yu map source network
There is also a "roasted sugar" process of Hetian jade, which is used to make the effect of beautiful sugar jade.
Source: ZiLong Zhai
Using high temperature to make a black paste-like color, simulating the natural sugar color, this "sugar color" is more dull, scorched black, this method is mostly used for lower-cost Korean materials.
<h1 class="pgc-h-arrow-right" data-track="51" > organic gemstones</h1>
Amber wax
Baked beeswax
In response to the demand of most consumers who like the top "chicken fat yellow" wax color, "smart" merchants have artificially baked the light color of beeswax to make the color of "chicken fat yellow" and sold it at a high price.
More commonly, there are so-called "old waxes", most of which are optimized by artificial baking. The baked color belongs to the physical optimization method in amber wax, not processing, and natural amber (beeswax) will be written when issuing a general appraisal certificate.
Baked blood perks
There are two kinds of blood perthr on the market, one is artificially roasted blood percussion, which is mostly baked with brown amber;
There is also a natural color, mainly Burmese blood perch.
Artificially roasted blood perks
ivory
Ivory heat treatment sometimes appears in antiques and literary play, the main purpose is to make the old, it seems to have a sense of age.
Many of the so-called "old ivory of the Qing Dynasty" were actually made only a few days ago.
(Note: The source of the figure in this article is partly from the network, invasion and deletion or contact the source of the editor's remarks)