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What is gemstone optimization treatment?
learn about its concept, history, and classification
Natural gemstones have a unique charm and have always been loved by people. Natural gemstones include natural gems, natural jade, and natural organic gems, characterized by beauty, durability, and rarity.
“Names of Gemstones” defines gemstones as a collective term for natural gemstones (including natural gems, natural jade, and natural organic gems) and artificial gemstones (including synthetic gems, artificial gems, assembled gems, and reconstructed gems), abbreviated as gems.
Gemstone optimization treatment aims to address the defects and shortcomings of natural gemstones, using artificial methods to improve their color and transparency, thereby enhancing the economic and practical value of the gemstones. It reprocesses and re-treates natural gemstones, fully utilizing and increasing their value.
Tartalomjegyzék
Section I The concept and main content of gemstone optimization treatment
Gemstone optimization treatment enhances natural jewelry stones’ practical and economic value. Certain technological processes and methods improve the color, transparency, special optical phenomenon, physical and chemical stability, etc., to compensate for the shortcomings of natural gemstones, thereby increasing their practical and commercial value. Gemstone optimization treatment, also known as gemstone improvement, refers to the enhancement of natural gemstones in terms of color, transparency, and optical effects. Therefore, the target of gemstone improvement is natural gemstones, which is a necessary means of enhancing the value of natural gemstones.
1. The concept of gemstone optimization treatment
The optimization treatment of jewelry stones refers to all methods used to improve the color, clarity, transparency, luster, or special optical phenomenon of jewelry stones, as well as their appearance, durability, or usability, excluding cutting, grinding, and polishing. Gemstone optimization treatment addresses the shortcomings and defects of natural gemstones, utilizing modern scientific and technological means to improve the quality of gemstones.
The optimization treatment of gemstones is an important aspect of gemology research, mainly aimed at improving the color and transparency of natural gemstones, especially those with poor color and transparency. Since each gemstone’s properties differ, the improvement experimental plans also vary greatly, and practical improvement methods must be formulated based on the color formation principles of different gemstones. The coloring mechanisms and color improvement of gemstones have become specialized research directions in gemology.
2. Differences and connections between natural gemstones, synthetic gemstones, and optimized treatment gemstones
The formation process of natural gemstones is very long, growing slowly under natural conditions, and possesses stable physical and chemical properties. Synthetic gemstones are crystals grown in a laboratory under conditions that simulate the growth conditions of natural gemstones. Synthetic gemstones are completely or partially artificially manufactured crystalline bodies, amorphous bodies, or aggregates with known corresponding natural counterparts with physical properties, chemical compositions, and crystal structures that are the same as those of the corresponding natural gemstones. The premise of gemstone optimization treatment is that natural gemstones have certain defects, such as light color, low saturation, poor transparency, etc. The target of optimization treatment is natural gemstones, which is an effective means of enhancing the value of natural gemstones. Therefore, the reprocessing and reprocessing of synthetic gemstones cannot be called the optimization of gemstones in the gemological field.
The optimization treatment of gemstones includes multiple aspects, such as upgrading low-grade gemstones to mid-high grade, improving the color and transparency of gemstones, and upgrading non-gem grade to gem grade, etc. The “Geuda” corundum from Sri Lanka, originally only used as a general ornamental stone, can be improved into beautiful gem-grade blue sapphires through artificial heat treatment, increasing its value by dozens or even hundreds of times.
3. Main methods of gemstone optimization treatment
The optimization treatment methods for natural gemstones include all technical methods that can enhance the value and usability of the gemstones. Of course, it should also include the processing and craftsmanship of the gemstones. People try to cut and polish the gemstones based on their natural shapes and physical properties to achieve the optimal usability of the gemstones. Coupled with the careful design and exquisite craftsmanship of artisans, these are all methods to enhance the value of gemstones. Especially for some precious gemstones, each piece of art embodies the designer’s hard work. The optimization treatment methods mainly include the following parts.
(1) Physical and chemical treatment of raw gemstone materials and finished products
Physical or chemical methods can be used to remove impurities from the surface of gemstones, for example, using strong acids to clean jade and removing dark and mixed tones from the surface to improve the color and transparency of the jade. B-grade jadeite is generally cleaned with strong acids before resin filling to remove surface impurities, and then resin filling treatment is performed.
(2) Using processing and craftsmanship techniques to turn waste into treasure (gemstone processing techniques)
The treatment methods in this area are mainly reflected in some crafts. As the saying goes, “Jade that is not carved does not become a vessel.” Ordinary crafts can create artistic treasures through the careful creation of master carvers. The processing and design of gemstones can maximize their usability, reflecting the exquisite qualities of each type of gemstone.
The methods of gem optimization treatment can be divided into broad and narrow definitions. Broadly, it refers to all technical methods that can enhance the value and utilization of gems. Narrowly, it refers to improving the chemical composition and defects within the gem, changing the color and transparency of the gem to make it more perfect. In this book, it refers to the narrow definition of treatment methods.
The gem optimization treatment methods referred to in this book do not include gem processing, craft utilization, and the design of crafts. The gem optimization treatment in this book refers to improving aspects such as color, structure, transparency, and special optical phenomenon of gems using certain processing equipment based on the principles of color presentation of common gems. It mainly targets natural gems, and common methods include heat treatment, irradiation, dyeing, filling, high-temperature, high-pressure treatment, diffusion, laminating or coating film, and bonding.
Just like meticulous manual carving, improving the appearance characteristics and stability of gems through narrow treatment methods, such as heat treatment and radioactive irradiation, can also enhance the economic value of the gems. A piece of translucent or opaque corundum material can only be used as an abrasive for grinding thin sheets or necklaces, and its value is negligible. However, if artificially treated, it could become a bright blue transparent gem with a value of several hundred to over a thousand yuan per carat.
(3) Content of gem optimization treatment
Gem optimization treatment mainly selects appropriate optimization treatment methods based on the causes of color in different gems. Not every gem can be improved through optimization treatment. The common improvement methods mainly include the following aspects: changing poorly colored gems into beautifully colored gems, improving low transparency to high transparency, upgrading low-grade gems to high-grade ones (increasing starlight, cat’s eye, etc.)， and upgrading non-gem grade to gem grade. These optimization treatment methods aim to enhance the utility and commercial value of gemstones, increasing and supplementing the value of natural gemstones.
(4) Issues related to the optimization treatment of gemstone attributes
The object of gemstone optimization treatment is natural gemstones, which enhance and increase the value of natural products. Natural gemstones and synthetic gemstones have both distinctions and connections: the distinction lies in their growth environments; natural gemstones grow in nature over a long period in complex environments, while synthetic gemstones are minerals synthesized in laboratories by simulating the growth conditions of natural gemstones, with a shorter growth time and not entirely consistent growth environments. The similarity between the two is that they are of the same mineral type and have fundamentally the same physical and chemical properties. Optimized gemstones belong to natural ones and do not include treated and processed synthetic gemstones.
4. The significance of gemstone optimization treatment
Due to the rarity of natural gemstones, they cannot meet the growing demand of people, and since there are very few perfect natural gemstones, there are bound to be some defects. Therefore, the technology for optimizing gemstone treatment has gradually developed, mainly for the following reasons.
(1) The demand for gemstones is gradually increasing.
Due to their unique charm, gemstones have become a popular type of decoration, collectible, and appreciation item throughout history and across cultures. With the development of science and technology and the improvement of people’s living standards, the demand for gemstones is growing. According to data from the National Bureau of Statistics, in 2002, the import and export value of gemstones in China was 84 billion USD, and combined with the import and export value of jewelry and pearls, it could reach 320 billion USD. By 2016, the import and export value of gemstones in China had reached 930 billion USD, with a growth rate far exceeding the international average. With the rapid economic development, the gemstone industry and jewelry market will become even more prosperous, and the demand for gemstones will also increase. The optimization treatment of gemstones can enhance their economic and commercial value, making the most of their utility and maximizing their effectiveness.
(2) Perfect and flawless natural products are extremely rare.
Due to the limited resources, the development speed of new gemstone deposits is far below the social demand, and perfect and flawless natural products are extremely rare. According to statistics on diamond production, on average, every 4 tons of ore mined from diamond mines can yield only 1 carat (0.2 g) of diamond rough, of which nine-tenths can only be used for industrial diamonds, and the remaining one-tenth, which is 0.1 carat (0.02 g), can be considered a better quality gemstone-grade diamond. Although the output of other colored gemstones is higher than that of diamonds, it still cannot meet the growing demand. The limitations of natural resources create a contradiction between supply and demand, determining that people must optimize the treatment of those low-quality natural gemstones, raising non-gemstone-grade rough to gemstone-grade, and improving the quality of inferior gemstones to meet society’s demand for natural gemstones.
(3) Technological advancements have driven the development of gemstone optimization treatment.
With the development of science and technology, the research on the optimization treatment of gemstones has become a specialized discipline, and the methods of optimization treatment are increasing. The initial gemstone optimization treatments were only heat treatment, irradiation, coating, and bonding methods. Many new optimization treatment methods have emerged, such as diffusion, coating film, and high-temperature high-pressure treatment. The variety of gemstones used for optimization treatment is also gradually increasing, and most common natural gemstones can be improved in quality through optimization treatment. The treatment methods are becoming more complex, and the appearance of optimized gemstones is very similar to that of natural gemstones, sometimes making it impossible to distinguish them using traditional identification methods. Therefore, identifying optimized gemstones has increasingly become an important research topic.
5. Process Requirements for Optimized Treated Gemstones
Natural gemstones possess the characteristics of beauty, durability, and rarity, while the requirements for optimized treated gemstones place more emphasis on the stability and durability of the physical and chemical properties of the gemstones. If the optimized treated gemstones are unstable, then this optimization treatment method is unsuitable for commercial production. Therefore, the optimized treated gemstones must meet the following conditions.
(1) Beauty
Beauty is a fundamental attribute of natural gemstones, and the outstanding ones among naturally produced gemstones possess alluring beauty, such as imperial topaz, pigeon blood ruby, green jade, and yellowish green emerald. The requirement for optimized treated gemstones is to bring various colors, textures, lusters, and transparencies of natural specimens closer to the most outstanding and beautiful ones, making them more akin to the most beautiful natural state. For example, transforming ox blood red (dark red) ruby into the natural color of pigeon blood red or treating light green jade into yellowish green.
(2) Durability
The durability of a gemstone refers to its stability. Natural gemstones generally have good stability; their color, transparency, and physical and chemical properties do not change over time. Gemstones that have been optimally treated must also possess this property to be put on the market. Durability mainly includes two aspects:
① The physical property stability of the gemstone. This means that the optimally treated gemstone’s hardness, toughness, and structural stability must be good. Improved gemstones often undergo wind and rain tests to verify their stability.
② The gemstone’s chemical stability includes resistance to heat, light, and chemical corrosion, such as not deteriorating or discoloring when exposed to sunlight, water immersion, or sweat. For example, turquoise that has undergone color-filling treatment may develop pittings or change color over time; colored agate necklaces may fade after being exposed to sweat, all of which can affect the sales and value of these gemstones.
(3) Harmless
Harmlessness includes the absence of toxic chemical components and no radioactive residues. Gems that have been optimized must be tested by relevant national institutions and meet national safety standards.
Harmful chemical components are often introduced into gems through chemical treatment methods. For example, soaking in solutions containing harmful chemicals or adding cinnabar to bloodstone, where the main component of cinnabar is HgS, with the mercury content approximately 86.2%, often mixed with realgar, apatite, and asphaltene. The mercury, arsenic, lead, and antimony in these materials harm the human body.
Gems improved by radioactive irradiation often retain radioactivity. Gems treated by irradiation must be tested, and only those with residual radioactivity below the specified standard can be marketed. For instance, most blue topaz on the market has been treated with irradiation, resulting in very stable colors. Still, after a year of irradiation treatment, they can only be sold once the residual radioactivity meets the standards.
Section II The History of Gem Optimization Treatment
The history of gem optimization treatment is long-standing, with some methods recognized in ancient times. For example, heat treatment, where it was discovered that heating could deepen the colors of gems like agate and chalcedony, improving less vibrant gems into bright ones and turning flawed gems into perfect ones. As people’s understanding of gemstone properties improved, so did the techniques for enhancing them. Some of these technologies may have been discovered by chance, while others have been passed down from folklore, making them rarely seen in literature. As people gradually understood the causes of color, structure, and physicochemical properties of common gemstones, new ways and methods for gemstone optimization treatment began to develop.
1. Ancient Gemstone Optimization Treatment
The main optimization treatment method for ancient gemstones was heating. As early as 2000 BC, heated red agate and sard appeared in India; in 1300 BC, dyed sard was found in Egyptian tombs. Traditional optimization methods such as coating and bottom filling also emerged early on.
By the 4th century AD, Egypt had written records of heating quartz or other gemstones to create fissures, then penetrating dyes into them, choosing the dye color according to the desired color.
Some have speculated about the methods of improving ancient gemstones. In ancient times, invasions and plundering wars occurred frequently between regions, often resulting in the burning of the deceased’s remains, and sometimes the gemstones burned with their owners became more beautiful. Thus, a set of heat treatment methods was gradually explored.
2. Improvements in Gemstones in Modern Times (15th to 19th century)
In the second half of the 15th century, handicrafts were very developed, and the jewelry industry, primarily manual, saw new developments. With advancements in techniques such as grinding and bonding, improvements and substitutes like layered and colored glass emerged; the development of chemistry and dyeing industries brought gemstone dyeing and filling to a new level; due to advancements in metallurgy, the temperature for gemstone heat treatment increased, leading to new developments in heat treatment techniques for gemstones.
Due to the deceptive nature of some improved gemstones, combined with the actions of unscrupulous merchants seeking profit without disclosure of “fakes” and the lack of knowledge among many jewelry enthusiasts on distinguishing them, improved gemstones gained a “mysterious” aura. This was particularly evident in the 16th and 17th centuries.
Without complete identification methods, the improvement of gemstones had a certain level of deception, such as using exploded crystals dyed red or green to impersonate rubies or emeralds and using burnt stones like zircon to impersonate diamonds. This caused social unrest, and people associated improving gemstones with deception. Therefore, in the 16th century century, Italian law prohibited gemstone dyeing. Even today, some still refer to improved gemstones as “fake,” which has hurt the gemstone market. As people’s understanding of jewelry and gemstones increases, they can correctly recognize the differences and values between natural gemstones, optimized treated gemstones, and synthetic gemstones, choosing suitable gemstones according to different needs.
3. New Developments in Optimized Treatment Techniques for Gemstones in Modern Times (20th and 21st Century)
Natural sciences made significant breakthroughs in the late 19th and early 20th centuries. With the maturation of gemology, the study of artificially enhancing natural gemstones to increase their value became a discipline.
People’s understanding entered the atomic level, using mineral structures and even quantum theory to explain gemstones’ color, transparency, and other physical properties. The analysis of the color origins of minerals and gemstones shifted from the macroscopic to the microscopic realm, introducing new techniques, equipment, and methods from various related fields into gemstone optimization.
In 1904, American scholar M. Beuer introduced the state of gemstone optimization in the early 20th century and provided some valuable detailed information in his book “Precious Stones.” The book described heating methods to fade smoky crystal and zircon and transform amethyst into citrine, yellow topaz into pink, and pink chalcedony into red.
In 1958, the Beijing Jade Factory began researching agate dyeing technology, completing experiments on dyeing agate red, green, blue, and black, and entering mass production. After 2000, high-temperature, high-pressure color-changing diamonds, diffusive sapphires with beryllium, assembled jade, and assembled nephrite began to appear in the domestic market. Modern gemstone optimization research has four prominent characteristics.
(1) The application of irradiation methods in gemstone optimization.
X rays, γ rays, and many radioactive methods have provided a new field for optimizing the processing of gemstones in physics. Irradiated gemstones are becoming increasingly common in the market.
In 1904, W. Crookes in the UK irradiated diamonds with radium as a medium, turning them green. Doelter pointed out in 1909 that some colors produced by radioactive radiation can lose their color under strong light; colorless fluorite can be irradiated to become purple, and pink topaz can be irradiated to become easily fading orange-yellow, also mentioning that heating can promote fading.
In recent years, new irradiation methods have emerged that can control the color of the products, such as changing diamonds to yellow, pink, or blue and changing colorless crystals to smoky or purple through irradiation. The types of gemstones that can be treated with irradiation have increased, such as tourmaline, aquamarine, beryl, feldspar, calcite, and spodumene, which can also be used to change the color of gemstones.
(2) Updates on heating treatment methods
In 1976, heating treatment methods improved the semi-transparent milky white corundum from Geuda, Sri Lanka, to a beautiful blue sapphire. This success in gemstone optimization treatment injected new vitality into thermal treatment methods. It then expanded to methods of heat treating colorless or light-colored sapphires to turn them yellow, orange-yellow, etc., and diffusion methods to add color or create starlight effects.
In 1979, the Thai mastered the heat treatment technology of rubies and sapphires with commercial value, improving dull-colored sapphires into beautiful blue sapphires. Most rubies and sapphires on the market are products of heat treatment. Heat treatment can be applied to almost all types of gemstones, and by controlling different oxidation-reduction conditions, the color of the gemstones can be effectively improved.
In recent years, there have been breakthrough advancements in gemstone research internationally every 2〜3 years, leading to the emergence of 75% colored gemstones in the market, with phenomena such as corundum ruby and corundum sapphire, around 80% being artificially optimized.
(3) The combined use of multiple treatment methods
In the optimization process of gemstones, multiple treatment methods are often used to improve the quality of the gemstones. For example, jadeite is bleached, filled, and dyed, commonly known as B grade or C grade products. This entire process changes both the structure and transparency of the jadeite, as well as its color; diffusion methods are commonly used for sapphires, topaz, tourmaline and other gemstones to enhance their color, but the depth of a single diffusion is very shallow, so multiple diffusion treatments are often used to strengthen the color concentration and depth of the gemstones; filling treatment is commonly used for structurally loose turquoise, but it is also dyed during the filling process, which increases both the color and stability of the gemstone.
(4) New methods for color-enhanced gemstones are constantly emerging.
New methods and technologies for color gemstones are constantly emerging, developing rapidly, becoming increasingly sophisticated, and frequently changing.
The renovation of old methods and the emergence of new methods constitute the new characteristics of gemstone optimization treatment during this period. Looking at the current state of research in the field of artificial optimization treatment of gemstones worldwide, there are three development trends in gemstone optimization treatment:
① The research and production of artificial optimization treatment of gemstones have gradually gained an equally important status as gemstone identification and processing. The types and varieties of gemstone improvements are also gradually increasing, as they can alleviate the contradiction between people’s demand for natural gemstones and actual supply; on the other hand, enhancing the aesthetic and economic value of gemstones through artificial means can also generate significant economic benefits and promote the development of the jewelry market.
② Using the most advanced modern analytical techniques strengthens theoretical research on the crystal structure, crystal chemistry, and color-causing mechanisms of gemstones, providing a theoretical basis for the artificial optimization treatment of gemstones.
③ The scope of objects for artificial optimization treatment of gemstones has greatly expanded, almost including all varieties of gemstones. In recent years, the jewelry market has seen a rich diversity of colored gemstone varieties, largely benefiting from improvements in artificial optimization treatment technologies and processes.
Since the 21st century, the means and methods for optimizing gemstones have been increasing. People can turn green beryl into blue aquamarine, colorless topaz into blue topaz, and colorless diamonds into yellow, green, blue, and pink diamonds, among others. The technology to transform low-quality corundum into blue or orange sapphires through heat treatment has recently become popular. It is reported that 80% of the colored gemstones sold in the international market have been optimized, and the optimization of corundum types, such as rubies and sapphires, exceeds 80%. Some improved gemstones have stable colors that do not change over time and are recognized as being of equal value to natural products.
While optimized gemstones have brought prosperity to the market, they have also led to negative effects. Some merchants deceive consumers by passing off optimized gemstones as natural ones, causing panic among consumers regarding the jewelry market. Therefore, it is necessary to strengthen the management of sellers and optimized gemstones, strictly name gemstones in the market according to national standards, and label optimized gemstones to gain consumer trust and promote the healthy development of the jewelry market.
Copywrite @ Sobling.Jewelry - Egyedi ékszergyártó, OEM és ODM ékszergyár
Section III Classification of Optimization Methods
1. Classification by Optimization Principles
Currently, many varieties of gemstones on the market have undergone artificial optimization, and the methods of optimization vary. Different optimization methods may be used for the same type of gemstone, and different gemstone varieties may also use the same optimization method. This book categorizes common optimization methods into three major categories with a total of twelve types based on the principles of optimizing gemstones, summarizing the currently common optimization methods with specific plans as follows:
First Category: Color Alteration Methods
① Heat Treatment: Heating colorless or light-colored gemstones to change or improve their color.
② Irradiation Method: Using radioactive irradiation to create color centers in gemstones, thereby changing their color.
③ Comprehensive Treatment: First irradiating with radiation, then performing heat treatment.
④ High Temperature and High Pressure: Using high temperature and high-pressure methods to modify the color of gemstones.
These four optimization treatment methods use relatively large instruments and equipment with strict processing conditions. The optimized treated gemstones have relatively stable physical and chemical properties, making them the most common optimization treatment method.
Second type: Chemical treatment method
① Dyeing and coloring;
② Bleaching;
③ Bleaching and filling;
④ Diffusion treatment.
These four types of treatments are obtained using chemical processing methods, the required equipment is simple, optimization is easy to carry out, and some gemstones become unstable after optimization.
The third type is physical treatment methods.
① Coating;
② Filling;
③ Laser drilling;
④ Bonding.
These four types of optimized treatments are all obtained using physical methods, with simple processing methods, clear characteristics after treatment, and easy identification. The twelve gemstone optimization treatment methods in these three categories cover all current methods of gemstone optimization treatment, with specific introductions to each method’s concept, optimization treatment principles and methods, scope, and common classification characteristics of optimized treatment gemstones.
(1) Szín alteration method
This optimization treatment method is the most important way to improve gemstones, mainly by changing the color, transparency, or other physical properties through heat treatment or radioactive irradiation. The principle is to artificially simulate the natural gemstone formation process based on the formation mechanism and mineralization conditions of gemstone minerals, thereby improving the physical properties of gemstone minerals. It is the same or similar to the principles of gemstone formation in nature, generally without adding chemical substances other than natural components.
The physical and chemical properties of gemstones after optimization treatment are stable (irradiated gemstones have some color instability), so these gemstones, after artificial optimization treatment, have an appearance similar to natural products. Heat-treated gemstones can be sold directly as natural gemstones without having to declare whether they have undergone artificial optimization treatment; except for irradiated crystals, irradiated treatments are classified as treated; high temperature and high pressure are mainly used for improving the color of diamonds, classified as treated. These gemstone optimization treatment methods can be divided into four types:
① Heat Treatment
Heat treatment is one of the most common gemstone optimization treatment methods. Almost all color-causing gemstones are improved in color through heat treatment, thereby improving the gemstones’ transparency. The principle is to change the content and valence state of the color-causing ions contained in the gemstone through different heat treatment conditions, thereby altering the physical properties of the gemstone, such as color and transparency, achieving the goal of improving gemstone quality. For example, the improvement of corundum sapphire is achieved through changes in the valence state or content of titanium and iron ions contained in the gemstone.
This optimization treatment method is mainly applied to the following gemstones: rubies, sapphires (blue, orange), star ruby and star sapphire, tanzanite, aquamarine (green to blue), zircon (blue or red), and yellow or green crystals obtained from amethyst processing.
② Irradiation method
This method utilizes radioactive irradiation, typically from sources such as cobalt-60, electron accelerators, or reactors, to irradiate gemstones with X-rays, γ rays, high-energy electrons, neutrons, protons, and deuteron, causing defects in the gemstones and creating color centers, which lead to changes in physical properties such as color variation, thereby improving the quality of the gemstones.
This optimization treatment method mainly applies to the following gemstones: smoky crystal, amethyst, purplish-red fluorite, and various irradiated diamonds (green, yellow, brown, black, blue, pink).
Some gemstones with improved colors using this method are unstable under normal temperature lighting and cannot be marketed as improved products. For example, irradiated yellow sapphires, deep blue cesium-lithium type tourmalines, brown topaz, purplish-red sodalite, and red tourmalines. Therefore, people should pay attention when selecting and using these gemstones.
③ Comprehensive Treatment Method
This method is mainly used for gemstones with color centers caused by color defects. It first involves radioactive irradiation, followed by appropriate heat treatment to change the physical properties of the gemstone (mainly color). Heat treatment aims to remove unstable color centers and obtain more stable ones. The treatment temperature generally does not exceed 300℃. To achieve the desired color, the heat treatment temperature must be strictly controlled, as different heat treatment temperatures may yield gemstones of different colors.
The commonly treated gemstone varieties using this method mainly include blue topaz, pink topaz, yellow crystal, blue-green tourmaline, and various colors of diamonds etc.
④ High-Temperature High-Pressure Method
The high-temperature, high-pressure method uses high temperature and high pressure to change the color of gemstones. The required equipment is complex, and the conditions are relatively strict. High temperature and high pressure generally refer to conditions where the temperature during gemstone optimization treatment is above 600℃ and the pressure is above 1 x 10°Pa. Currently, this method is mainly suitable for changing the color of diamonds.
The four types of color treatment methods for gemstones mentioned above are currently the most common optimized treated gemstones on the market. These optimized treated products are also the most popular, as their improved color and physical-chemical properties are stable. The prices of these gemstones are comparable to or slightly lower than those of natural gemstones.
(2) Chemical Treatment Method
The chemical method refers to adding a certain amount of chemical reagents, which react chemically with the components in the gemstone, allowing coloring elements to enter the gemstone lattice, thereby improving the gemstone’s color. Common chemical optimization treatments include dyeing and coloring, bleaching, and filling, diffusion treatment, etc.
① Dyeing and Coloring
This method typically uses organic dyes or inorganic pigments to soak or fill gemstones with many fissures; the solvents used are water or ethanol. Some gemstones, such as rubies and emeralds, can also use oil as a solvent. The color generally penetrates the gemstone along the fissures or tiny pores. The dyeing materials mostly have natural pores, such as chalcedony, agate, jade, marble, etc. If there are no natural pores, artificial methods, such as quartz explosion dyeing, can be used to create cracks.
This optimization treatment method suits natural gemstones with many fissures, such as rubies, sapphires, emeralds, jade, agate, chalcedony, tourmaline, spinel, crystal, turquoise, quartz and others.
② Bleaching
Bleaching gemstones generally involves using chemical agents with bleaching properties, such as chlorine and hydrogen peroxide, to bleach organic gemstones like pearls, ivory, and coral, removing internal discoloration to enhance the whiteness of the gemstones. This treatment method is commonly used for natural or cultured pearls that are particularly dark in color or have a greenish tint.
③ Bleaching and Filling
Most jade stones, such as jadeite and chalcedony, become porous after bleaching, and in addition to bleaching, they also require filling to make their structure more solid. The filling materials are generally organic glue, resin, plastic, etc. Other gemstones that can be bleached and filled include coral, ivory, silicified wood, and tiger’s eye.
④ Diffusion Treatment
Diffusion treatment refers to allowing foreign elements to enter gemstones under certain temperature conditions to change the color of the gemstones or produce special optical phenomenon. Diffusion treatment was initially used to improve the color and starlight effect of sapphires, and its application range has now expanded to include sapphires, rubies, topaz, tourmaline, and other gemstones.
(3) Physical Treatment Methods
Physical treatment methods refer to how natural gemstones are given an overall appearance through surface coating, bonding, filling, etc., mainly used to improve the color or stability of the gemstones. They can be divided into the following types.
① Coating
Coating involves applying a thin film to part or all of the gemstone’s surface, which can create a strong luster and cover up flaws, mainly reducing the surface’s diffuse reflection. This film can be colorless or colored wax, varnish, or synthetic resin, with a typical thickness of around 0.1μm. Gemstones with coatings have a good surface luster and increased hardness, which can enhance their value. In addition to coatings, a new film deposition technology has emerged in recent years, allowing for the deposition of certain metal oxides or diamond films onto the gemstone surface as needed, such as diamond coating, which involves applying a layer of synthetic diamond film onto the surface of natural diamonds. The initial films are mostly polycrystalline and relatively easy to identify.
The gemstones that can benefit from this technology include amber, chalcedony, diamond, pearl, shell, opal, jade, etc.
② Filling
Filling, also known as injection, is a technique that involves filling colorless or colored wax, oil, plastic, and other materials into the fissures of gemstones. Optimization treatment aims to remove the cracks in the gemstones, making the gemstone material more stable and increasing its value. For example, injecting colored or colorless resin into the porous structure of loose turquoise makes the turquoise texture harder; it is also possible to fill worthless chalky opal to create a significant iridescence effect.
The gemstones that can benefit from this technology include ruby, sapphire, emerald, turquoise, lapis lazuli, opal, jade, quartz, chalcedony, etc.
③ Laser Drilling
This method is mainly applicable to diamonds and oriental jasper. If there are black or dark inclusions in the diamond, localized laser drilling is needed to remove the inclusions, improving the diamond’s color and clarity. Laser drilling also applies to oriental jasper, where lasers create tiny holes in the gemstone or material (such as oriental jasper). Then, dye is injected to increase the “blood” content of the oriental jasper.
④ Assembly
Assembled gemstones are jewelry made by manually joining two or more pieces of material to create a cohesive impression. Depending on the materials, methods, or finished products, assembled gemstones can be categorized into several types: layered, backing, and encrusted. Assembled gemstones can be natural or synthetic and must be named based on the different gemstone materials or main materials used.
- Layered and backing stones This type of gemstone is formed by combining and bonding several materials, giving the appearance of a single gemstone. Some of these materials are gemstones, while others are substitutes like glass or plastic. Layered stones are generally a combination of three materials, bonding three different materials together to form a gemstone; backing stones are generally a combination of two materials, bonding two pieces together to form a gemstone. This technique has been developed for a long time, and many methods exist. Some unscrupulous merchants often use these types of gemstones to impersonate natural gemstones, doing so very discreetly, with various forms and types, mostly made into finished gemstones, requiring careful identification when purchasing.
- Encrusted stones: This type of gemstone grows additional gemstones on a natural or synthetic gemstone. The encrusted material can be thin or thick, related to synthetic gemstones. The thin layer of gemstone that grows on the gemstone is usually called encrusted stone, with no strict boundary between it and the thick artificial crystals. This method is often used to grow a layer of synthetic emerald on beryl or quartz.
In addition to the twelve optimization methods summarized above, new technologies and methods continue to emerge, adding many new varieties to optimized gemstones. There are also cases where multiple methods and techniques are applied simultaneously, such as B+C for jadeite and multiple diffusion treatments for sapphires.
2. Gemstones optimized methods
There are many types of optimized gemstones on the market, and with the advancement of technology, the optimization methods are also increasing, potentially combining several treatment methods. the optimization of gemstones is divided into two main categories: optimization and treatment. Optimized gemstones can be directly named using the names of natural gemstones, while treated gemstones must indicate the treatment or specific treatment method. The distinction between optimization and treatment is significant for improving gemstone quality.
(1) Enhancing
Enhancing refers to traditional, widely accepted optimization methods that can reveal the potential beauty of jewelry and gemstones, including heat treatment, bleaching, waxing, soaking in colorless oil, and dyeing (for chalcedony and agate).
① Heating
Heating is a method of heating samples by artificially controlling conditions such as temperature and the oxidation-reduction environment. Its purpose is to improve or change gemstones’ color, clarity, and special optical effects.
The heat treatment process involves placing gemstones in a high-temperature furnace, using conditions such as oxidation, reduction, or vacuum to change the content and valence state of the color-causing ions within the gemstones, thereby altering their physical properties such as color and transparency to varying degrees.
Many types of gemstones are suitable for heat treatment, such as rubies, sapphires (blue, orange), tanzanite, aquamarine (green to blue), zircon (blue or red), and yellow or green crystals obtained from treated amethyst, among others.
② Bleaching
Bleaching is the process of soaking samples in chemical solutions to lighten the color of gemstones or remove discoloration. Generally, bleaching agents such as hydrogen peroxide bleach organic gemstones like pearls remove discoloration and increase whiteness.
③ Waxing
Waxing is the process of immersing wax into the surface gaps of gemstones to improve their appearance. Most gemstones, such as turquoise, lapis lazuli, and serpentine, use this method.
④ Colorless oiling
Colorless oiling is the process of soaking colorless oil into the gaps of gemstones to improve their appearance. This method mainly targets gemstones with many fissures, such as emeralds, rubies, and opals.
(2) Treating
Treating is a non-traditional yet not widely accepted optimization method. It includes color oiling, filling (with hard materials like glass), dyeing, irradiation, laser drilling, coating, diffusion, and high-temperature, high-pressure treatment.
① Colour oiling treatment
Color oiling treatment involves soaking color oil into the gaps of gemstones to improve their appearance. This method is commonly used for rubies, emeralds, and opals.
② Filling Treatment
Filling treatment is filling the gaps and holes of porous gemstones with curing materials such as Pb and Bi glass, artificial resins, or other polymers to change their durability and appearance. It is commonly used for natural gemstones with many fissures or loosely structured stones, such as rubies, jade, turquoise, and emeralds.
③ Colour Dying
Colour dying is the process of allowing coloring substances to penetrate gemstones to produce color, enhance color, or improve color uniformity. It is commonly used for chalcedony, agate, jade, and marble. If there are no natural cracks, artificial methods, such as quartz explosion dyeing, can be used to create cracks.
④ Irradiation
Irradiation is usually performed using radiation sources such as cobalt-60, electron accelerators, or reactors to irradiate gemstones, causing defects and the appearance of colour centers, which leads to changes in the color of the gemstones. This improvement method suits smoky crystal, amethyst, purple-red fluorite, and various irradiated diamonds. The irradiation treatment of quartz is classified as optimization.
⑤ Laser drilling treatment
Laser drilling treatment is mainly used to improve the clarity of diamonds. A laser beam and chemicals remove dark inclusions from within the diamond, leaving laser marks, with tubular or funnel-shaped laser marks referred to as laser holes. Laser drilling can also be used for oriental jasper.
⑥ Coating
Coating uses coating, plating, filling, and other methods on the surface of jewelry covered with film to change the luster of jewelry jade, color, or produce special phenomenon. Such as diamond coatings, yellow jade coatings, etc.
➆ Diffusion
Diffusion allows coloring elements to penetrate the surface layer of gemstones under high-temperature conditions, producing color and/or starlight effects. For example, sapphire can appear blue after cobalt ion diffusion and red after chromium ion diffusion, and starlight effects can also be produced through diffusion.
➇ High-temperature and high-pressure treatment
High-temperature and high-pressure treatment (HPHT) transforms type IIa brownish-yellow diamonds into colorless diamonds or changes type Ia brown diamonds into yellow-green, yellow, and other colored diamonds under high-temperature and high-pressure conditions.
The optimization treatment of gemstones is an important topic in gem research. With the advancement of technology, new optimization treatment methods are continuously emerging, bringing certain difficulties and challenges to gem identification. Referring to the classification of gemstone optimization treatment methods in “Gemstone Names” (GB/T 16552-2017), the common optimization treatment methods, categories, and applicable gemstone types are shown in Table 1-1.
Table 1-1 Common optimization treatment methods, categories, and applicable gemstone types
| Optimalizáló kezelési módszerek | Kategóriák | Megjegyzés: | Applicable gemstone types |
|---|---|---|---|
| Hőkezelés | Optimalizálás | Gemstones change color and transparency by altering the valence state and quantity of chromophore ions through heating under redox conditions. | Ruby, sapphire, emerald, crystal, tourmaline, zircon, topaz, tanzanite, jade, agate, chalcedony, and fluorite. |
| Fehérítés | Optimalizálás | Acidic solutions remove color variations in gemstones. | Jadeite, quartzite, pearls, corals, etc. |
| Lézeres fúrás | Kezelés | Using lasers to remove inclusions from gemstones locally | Diamonds, oriental jasper, etc. |
| Fehérítés, tömés | Kezelés | After cleaning with acidic solution, fill with glue, resin, and other materials | Jadeite, quartzite jade, coral, etc. |
| Töltő | Optimalizálás | Fill gemstones with colorless oil and wax, use a small amount of resin to fill the gaps in gemstones, slightly altering their appearance. This method for emeralds is for clarity optimization and is classified as optimization (should include a note). | Ruby, sapphire, emerald, tourmaline , crystal, jade, turquoise, lapis lazuli, malachite, marble, Qingtian stone, Shoushan stone, opal, chalcedony, etc. |
| Optimization (should include explanatory notes) | Fill small cracks and voids in gemstones with glass and artificial resin to improve their durability and appearance. | Ruby, sapphire, emerald, tourmaline , crystal, jade, turquoise, lapis lazuli, malachite, marble, Qingtian stone, Shoushan stone, opal, chalcedony, etc. | |
| Kezelés | Injecting porous or cracked gemstones with solidifying materials such as glass containing Pb Bi and artificial resin to change their durability and appearance | Ruby, sapphire, emerald, tourmaline, crystal, jade, turquoise, lapis lazuli, malachite, marble, Qingtian stone, Shoushan stone, opal, chalcedony, etc. | |
| Bevonat | Optimization (should include explanatory notes) | Coating the surface of natural organic gemstones with a colorless film to change their luster or provide protection | Diamond, emerald, beryl, tourmaline, topaz, crystal, feldspar, jade, opal, marble, fluorite, coral, etc. |
| Kezelés | Coating the surface of natural gemstones with a colorless or colored film to change their color or produce special effects | Diamonds, emeralds, beryl, tourmaline, topaz, crystal, feldspar, jade, opal, marble, fluorite, coral, etc. | |
| Magas hőmérséklet és magas nyomás | Kezelés | - | Diamond |
| Festés | Kezelés | This method of jade optimization | Rubies, emeralds, jade, nephrite, agate, chalcedony, quartzite, etc. |
| Sugárzás | Kezelés | This method of crystal optimization | Diamonds, sapphires, beryl, tourmaline, zircon, topaz, crystal, pearls, etc |
| Diffúzió | Kezelés | The addition of coloring ions under high-temperature conditions allows the coloring ions to enter the gemstone lattice. | Ruby, sapphire, topaz, etc |
(3) Optimize the naming rules for gemstones.
To scientifically and accurately describe the characteristics of gemstone enhancement treatments, better regulate the jewelry and gemstone market, and protect consumer interests while also considering the naming conventions of the business community and traditional names as well as internationally accepted names and rules, the country has established a series of national standards for the jewelry and gemstone industry.
① Optimized Naming of Jewelry and Gemstones
The optimized representation method should meet the following requirements:
- Directly use the names of gemstones, and specific optimization methods can be noted in the relevant quality documents, such as heat-treated rubies, dyed agates, etc.
- Some gemstones should have specific optimization methods noted in the relevant quality documents after optimization, and the degree of optimization can be described, such as: “filled” or “light/moderate filling.”
② Naming of treated gemstones
For processed gemstones, the description method should meet the following requirements:
- Indicate at the basic name of the gemstone that the specific treatment method is added before the name, such as diffusion sapphire, bleached, filled jade; add parentheses after the name to indicate the treatment method, such as sapphire (diffusion), jade (bleached, filled); add parentheses after the name to indicate the word “treatment,” such as sapphire (treatment), jade (treatment); specific treatment methods should be noted in relevant quality documents, such as diffusion treatment, bleaching, filling treatment.
- For gemstones whose treatment status cannot be determined, it may not be indicated in the name, but it should be noted in relevant quality documents that “may have been X X treated.”
- Treated synthetic gemstones can be directly named using the basic name of synthetic gemstones.
- Gemstones treated by multiple methods or whose specific treatment methods cannot be determined should be named according to the rules above. It can also be noted in relevant quality documents that ” XXX has been artificially treated,” for example, diamond (treatment), with a note stating “diamond color has been artificially treated.”
③ Naming method for assembled gemstones.
- Write out the names of the constituent materials layer by layer, adding the words “assembled stone” after the name of the constituent material, such as “sapphire, synthetic sapphire assembled stone,” or using the name of the top layer material followed by “assembled stone,” such as “sapphire assembled stone,” or assembled sapphire, synthetic sapphire.
- For assembled stones made of the same material, add the words “assembled stone” after the name of the material, such as “zircon assembled stone.”
- For assembled stones primarily made of natural pearls, pearls, opals, or synthetic opals, use the names assembled natural pearl, assembled pearl, assembled opal, or assembled synthetic opal without listing the materials layer by layer.
- Naming method for reconstructed gemstones. Add the word “reconstructed” before the basic name of the natural gemstone. For example, “reconstructed amber” or “reconstructed turquoise.”
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