From the classification point of view, according to the differences of human factors and the specific characteristics of products, artificial products are divided into synthetic gems, artificial gem, assembled gems and recycled gems. (1) Synthetic gemstone: refers to a crystalline or amorphous substance partially or completely made by human beings, whose physical properties, chemical composition and crystal structure are basically the same as the corresponding natural gemstone. For example, synthetic rubies and natural rubies are both composed of Al2O3 (containing trace element Cr), with the same refractive index and hardness; ② artificial gem: refers to artificially made crystalline or amorphous substances, but these substances have no natural counterpart. Such as artificial strontium titanate, which has not been found in nature so far; ③ Assembled gemstone: refers to a gemstone that is made up of two or more materials by artificial methods and gives people the impression of overall cutting in appearance. For example, a popular sapphire faceted gem, often the upper part is synthetic sapphire, and the lower part is natural sapphire. The two are bonded by resin and look like a complete faceted gem. (4) Reproduction of gems: Some natural gems are artificially fused. Common ones are recycling amber and turquoise. The biggest difference between synthetic gemstones and artificial gem lies in whether the materials they produce have natural counterparts. ? Below, we will briefly introduce the materials, characteristics and simple identification methods of some common synthetic gems. Glass: Glass is a kind of low-priced artificial gem, which is used to imitate natural jewels and jade, such as chalcedony, timely, beryl (emeralds and aquamarine), jadeite, nephrite and topaz.
Generally speaking, it is relatively easy to distinguish between glass and precious stones. Gemstones are all crystals, which transfer heat faster, while glass is amorphous without crystallization, which transfers heat more slowly. Therefore, when touching the sample by hand, natural gemstones have a cold feeling, while glass has a warm feeling. It is more sensitive to judge whether it is cold or warm with the tip of the tongue sample, yes. In addition, observing with a magnifying glass, there are often curved or swirling fine lines on the surface and inside of the glass, which looks like the phenomenon that honey or glue is mixed unevenly when it is poured into clear water. There are all kinds of bubbles in the glass, such as round beads, ellipses and flat beads, which can be easily observed with a magnifying glass.
Plastic: Plastic is an artificial material, which is composed of long-chain polymer molecules. As an imitation of precious stones, plastics are mainly used to imitate opaque precious stones such as turquoise, jadeite, nephrite and ivory, translucent precious stones such as tortoise shell, pearl and shell, and transparent precious stones such as amber. ? According to the characteristics of plastics, such as low density (obviously lighter when weighed by hand), low hardness (which can be scratched with a knife), low conductivity (which feels warm) and flammability (when a sample is touched with a hot needle, the sample will melt or burn, giving off a pungent and unpleasant smell), it is easy to distinguish between gems and plastics. Synthetic cubic zirconia: Synthetic cubic zirconia is also called "CZ diamond" because it was first synthesized by the former Soviet Union and successfully put on the market as a counterfeit diamond in the 1970s. Also known as "Soviet diamonds" (this name has been abolished). The properties of artificial cubic zirconia are very close to those of diamond. First of all, its refractive index is as high as 2. 17, and its dispersion is 0.06, which is very close to 2.42 and 0.044 of diamonds. In particular, its high dispersibility makes the color flash of polished gemstones more beautiful. The Mohs hardness of synthetic cubic zirconia is 8.5, only slightly lower than that of ruby and sapphire, which can make the polished edge sharp and perfect, and the shiny and smooth surface is not easy to be scratched and sanded. Moreover, cubic zirconia can be synthesized to produce products with excellent transparency and complete colorless. In this way, after grinding it into a round diamond-shaped prismatic stone, its appearance is exactly the same as that of a diamond, and it is almost indistinguishable. Besides colorless and transparent cubic zirconia, bright red, yellow, green, blue, purple and purplish red products can be obtained by adding a small amount of color-developing elements into the composition. Although the artificial cubic zirconia looks like a diamond when it is ground into a gem, it can still be distinguished by some simple methods. The specific gravity of artificial cubic zirconia is about 6, which is 1.7 times that of diamond, so it feels heavy. Or use an oily pen to scratch the surface of the sample, leaving clear and continuous lines when scratching the diamond surface, and discontinuous small droplets appear when scratching the synthetic cubic zirconia; Or breathe into the sample. The sample with fast fog dispersion is diamond, and the sample with slow fog dispersion is synthetic cubic zirconia. Of course, to distinguish accurately, it is best to use instruments to identify, such as reflectors, thermal conductivity meters, microscopes and so on. As for real synthetic diamonds, because their synthetic cost is higher than natural diamonds, and synthetic diamonds are often fine and can't reach the level of gems, people don't have to worry about buying synthetic diamonds in the jewelry market at least for now. Synthesis of Ruby and Sapphire: The experiment of synthesis of ruby and sapphire began in 65438+60' s, but it was not until the birth of Werner furnace in the early 20th century that the synthesis of ruby and sapphire was really successful. Artificial ruby is crystallized from the melt, and its main component is Al2O3. When adding a little Cr, it will appear red, that is, synthetic ruby. If a small amount of Ti is added, it becomes artificial sapphire. Synthetic rubies and sapphires are very similar to natural rubies and sapphires in appearance and properties, so it is difficult to distinguish them. At present, identification is mainly based on the differences of inclusions in samples, such as synthetic rubies and sapphires, which often contain bubbles and tiny arcs. If the inclusions are small, these phenomena may not be observed with a magnifying glass, and they need to be observed with an optical microscope to distinguish them. Synthetic crystals are much richer in rock crystal resources than other precious stones. In the past, synthetic crystals were mainly used to meet the needs of telecommunications, optics and other industries, and it was not economical to use synthetic crystals as gems. However, with the decrease of natural resources and the improvement of synthetic technology, synthetic crystals are also widely used in jewelry.
There is almost no difference between synthetic crystal and rock crystal. The composition of the synthetic crystal is mainly silicon dioxide. Adding different trace elements can present varieties of different colors (such as colorless, purple, yellow, blue, green, brown, etc. ), but purple is the most widely used in jewelry, followed by yellow; There is not much difference in price between the two.
At present, the main method to distinguish synthetic crystals from rock crystals lies in their internal inclusions, which can also be measured by some simple instruments such as absorption spectrum. In addition, if you see blue or green crystals, you can usually judge that they are synthetic, because these two colors of crystals can hardly be found in nature.