I. Classification and Basic Characteristics of Gems Broadly speaking, gems are the general name of nature and artificial gem, referred to as gems for short. It covers all natural and artificial jewelry and jade, including all minerals, rocks and organic materials that meet the technological requirements.
1. Classification In order to standardize the classification of gemstones in China, China has formulated a unified gemstone classification scheme. China's national gemstone classification system fully considers the universality and habitude of the world, and tries to adopt the internationally widely used and increasingly unified classification principles. At the same time, in order to highlight the traditional characteristics of gem classification in China, jade is classified separately by combining international and domestic methods.
(1) Natural gemstones Natural gemstones mainly refer to natural gemstones, natural jade and natural organic gemstones. , and are the main gem ornaments in the market. In the field of gem circulation, unless otherwise specified, gems usually refer to natural gems.
Natural gemstones refer to mineral single crystals (including twins) which are produced in nature, beautiful, durable, rare and have certain technological value, and can be processed into ornaments. Generally, it has bright colors, high transparency, high hardness and stable chemical properties. Such as diamonds and rubies.
Natural jade refers to the mineral aggregate produced in nature, which has the characteristics of beauty, durability and rarity. It can be processed into decorations, and a few of them are amorphous. Such as jadeite and nephrite.
Natural organic gemstones refer to materials that are generated by natural organisms and partially or completely composed of organic substances, and can be used for processing into jewelry and decorations. Such as amber, coral, pearls, coal essence, ivory and so on.
(2) Artifacts Artifacts Artifacts refer to materials produced or manufactured by people in whole or in part and used for jewelry and decoration, mainly including synthetic gemstones, artificial gem, divided gemstones and recycled gemstones. Synthetic gem refers to a crystalline or amorphous substance that is completely or partially made by human beings and has a known counterpart in nature, and its physical properties, chemical composition and crystal structure are basically the same as the natural gem of the counterpart. Such as synthetic diamonds and synthetic sapphires.
Artificial gem refers to an artificial crystal or amorphous body, and there is no known counterpart in nature. Such as artificial yttrium aluminum garnet and artificial strontium titanate.
Split gem refers to a gem that is made of two or more materials by hand, which can give people an overall impression. For example, natural sapphire and synthetic sapphire are spliced together.
Recycled gemstones refer to jewels and jade with overall appearance that are welded or pressed by artificial means from fragments or chips of natural gemstones. For example, by pressing amber chips.
Knowledge Link China National Gemstone Classification System National Gemstone Quality Supervision Center divides gems into two categories, namely natural gems and artificial products.
Natural jewelry jade includes: natural gems (such as diamonds, rubies, sapphires, emeralds, opals, aquamarine, etc. ), natural jadeite (such as jadeite, nephrite, dushan jade, timely jade, etc. ) and natural organic gems (such as pearls, corals, amber, coal essence, etc.). ).
Man-made products can be divided into four categories: synthetic gems (such as synthetic diamonds, synthetic rubies, synthetic emeralds, etc. ), artificial gem (such as synthetic yttrium aluminum garnet, synthetic strontium titanate, etc. ), divided gems (such as opal, sapphire, etc.). ) and recycled gems (such as recycled amber and turquoise). ).
In addition, there is a special category, that is, imitation gems (such as imitation pearls, imitation crystals, imitation jadeite, etc. ), but it is not a real gem.
A reconstructed amber with a complete amber illusion.
(3) Imitation gems include these kinds of gems, which are only artificial gem used to imitate the color, appearance and special optical effects of similar natural gems, and natural gems used to imitate another natural gem. Such as using colorless natural zircon to imitate natural diamonds.
2. Value factors Gemstones are expensive, and high-grade and high-quality gems are even more valuable. During the Spring and Autumn Period and the Warring States Period, the King of Qin was willing to exchange 15 city for Zhao's treasure of "He Shi Bi". It can be seen that the value of gems is amazing, even because a gem can trigger a war.
Knowledge connects the determinants of the value of gems. First of all, it should be attributed to nature, especially the naturally occurring mineral rocks.
Second, it's beautiful. If a gem is not beautiful, it cannot be called a gem. The more beautiful, the more expensive.
Third, it is durable. For gems, the more durable the gem, the more expensive it is.
Fourth, scarcity. Scarcity plays a very important role in determining the value of precious stones. As a gem, the less output, the greater demand and the higher value.
Fifth, it is demand. Demand is also one of the factors that determine whether a gem is expensive. If the demand is too large, it will lead to snapping up, snapping up and raising the price.
Sixth, it is convenient to carry.
3. Basic characteristics As precious ornaments, gems should generally have beautiful, durable and rare characteristics. In addition, it must be small and exquisite, portable, fashionable, easy to store and transfer, and can play a role in maintaining and increasing value.
(1) Beauty, sparkling, gorgeous, dazzling, magnificent and beautiful are the first conditions to reflect the value of gems. Gemstones are usually bright in color, crystal clear, or have unique optical effects; The main feature of jadeite is its delicate texture, and it has a moist and bright aesthetic feeling after polishing.
Gemstones can be divided into colored gems and colorless gems by color. Among them, colored gems generally requires bright, soft, pure and uniform colors. For example, rubies, sapphires and emeralds are pure and gorgeous red, blue and green respectively; Colorless diamonds can show different spectral colors if they are cut and ground, which is called "fire color", commonly known as "fire"; Opal itself has a variety of color points, giving people a beautiful visual impact. Although colorless gemstones have no bright colors, they generally have strong luster and high transparency. Some colorless gems can produce special optical effects such as cat's eye, starlight, discoloration and swimming color after processing. "One stone can't be polished into a treasure", and the beauty of most gems is potential, which can only be fully displayed after proper processing.
(2) Durability Many precious stones are used for jewelry, and people will inevitably rub against other items when wearing them. Therefore, most gems need to have certain hardness, toughness and chemical stability, so that the gems on jewelry will not lose their luster because of wearing.
(3) Sparse is "rare, rare is expensive", which is a well-known truth. The rarity of precious stones includes both the rarity of varieties and the rarity of quality. One of the reasons why diamonds are expensive is that they are rare. Exquisite emeralds are extremely rare, so high-quality emeralds may be more expensive than a diamond of the same size and quality.
In addition, the change of GEM output determines the change of price. When natural amethyst was only found in Europe, it was considered as a rare and precious gem, and it was expensive. However, when Brazil developed a large-scale amethyst deposit, its price dropped sharply. Synthetic gemstones and natural gemstones are the same in nature, but they are generally quite different in price.
Important properties of gems 1. Gemstones of different colors are generally different in color. Even the same color can't be exactly the same in features and shapes, and there are often differences in shades and shades.
2. Hardness The durability of a gem depends largely on its hardness. Hardness refers to the degree of wear resistance of gemstones, or the reflection of other substances after scraping, grinding and rubbing.
3. Transparency refers to the ability of a gem to transmit light. Generally speaking, a gem with a thickness of two millimeters shall prevail. Light is called "transparent" when it is completely transmitted, "translucent" when it is partially transmitted, and "opaque" when it is basically opaque or completely opaque. Generally speaking, the higher the transparency of the same gem, the more precious it is.
4. Glossy luster is the surface phenomenon that gems directly reflect light to people's eyes. Brightness is a manifestation of the beauty of a gem, and the brightness of a transparent gem is related to its luster, which is an important criterion to judge the brightness of a gem.
5. Density is the main physical property of gemstones. Different gems have different fixed densities, and different gems can be distinguished according to different densities.
6. Fluorescence and Phosphorescence Many gemstones emit various colors of visible light when irradiated or heated by some special light sources. When the above-mentioned external conditions disappear, the luminescence phenomenon of gems also disappears, which is called fluorescence. After the external conditions disappear, gems can still glow for a long time, which is phosphorescence.
7. Inclusions In the process of gem growth, foreign substances or small crystals (solid, liquid, gas or mixture) are often mixed with accumulated substances and appear in an irregular form, that is, inclusions. In nature, gems generally contain a certain amount of inclusions.
8. The decomposition of dispersive white light into spectral colors is called dispersion. Various gemstones have different abilities to decompose light into various colors, so their dispersion is also different.
9. Cleavage and fracture cleavage, also known as "cleavage", are the inherent properties of crystals or grains splitting into planes in a certain crystallization direction under the impact of external forces; The fracture surface is that minerals do not fracture in a certain crystallization direction under the impact of a certain external force, but form a fracture surface. Different gems have different cleavage and fracture.
10. Birefringence and polychromatic birefringence are the phenomena that a beam of light enters an anisotropic crystal, splits into two beams and refracts in different directions. It is mainly divided into hexagonal, tetragonal, monoclinic, triclinic and orthogonal crystal systems, while the minerals in amorphous and equiaxed crystal systems are single refraction; Polychromaticity of minerals refers to the property of changing colors according to different incident light sources and incident angles.
II. Naming Principles of Gems For a long time, there is no uniform principle and standard for the naming of gems in the international jewelry industry, and there are various methods, even the names of the same gem are different.
Traditionally, gemstones are named by their colors, such as ruby, sapphire, aquamarine and amethyst. Named after special optical effects, such as cat's eye and golden star stone; Named after the place of origin, such as xiuyan jade named after the place of origin of serpentine jade and Hetian jade named after the famous place of origin of nephrite; Named directly after minerals and rocks
The naming rules of gemstones stipulated in Chinese national standards directly adopt the basic names of natural gemstones or their mineral names, without adding the word "natural", and the place of origin does not participate in naming. It is forbidden to use names composed of two or more natural gemstone names, and it is forbidden to use ambiguous commercial names.
Jade directly uses the basic name of natural jade or the name of its minerals and rocks, and the word "jade" can be added after the name of natural minerals or rocks, except natural glass. In particular, it is not allowed to use "jade" or "jade" alone instead of specific natural jade names.
Organic gemstones directly use the basic names of natural organic gemstones, and the names of natural organic gemstones are not modified by the place of origin.
Synthetic gemstones must be prefixed with the word "synthetic" in their corresponding natural gemstone names, and it is forbidden to use the names of manufacturers and manufacturers to name them directly.
Artificial gem needs to add the word "man-made" before the name of the material, and it is forbidden to use the name, manufacturer and mode of production of the manufacturer.
To assemble a gem, you need to write the names of the constituent materials layer by layer, and add the word "assembly stone" after the name of the constituent materials; Or add the word "split stone" to the name of the top material.
Natural gemstones must be preceded by the word "re-creation".
Imitation gems need to be preceded by the word "imitation".
Names (this is a scientific and accurate method commonly used in the international jewelry industry), such as spinel, beryl, olivine and so on. The adoption of some traditional names handed down from generation to generation, such as jade and amber, is often related to some ancient legends; Named after the manufacturer, production method, style, process name and enterprise name, such as Chatham Emerald, ruby with cosolvent method, etc. But this naming method is forbidden in China.
There are various naming methods in the world, and the naming of precious stones is inaccurate and vague, which leads to confusion in the naming of some precious stones. In order to better regulate the domestic gem and jade circulation market, China National Gemstone Quality Supervision and Inspection Center, on the basis of taking into account the commercial and traditional naming habits, drafted the National Gemstone Name (GB/T 16552-2003), which stipulated the naming rules of gem and jade.