About the author: Pan, member of the 3rd insurance institute of china Artificial Products Professional Committee, director of Shanghai Wanbaoda Craft Factory.

According to various archaeological excavations, early humans wore necklaces and ornaments such as shells, animal teeth and gravel. As early as the Han Dynasty, people used all kinds of lapis lazuli, malachite and agate as decorations embedded in bronzes, showing the close relationship between gems and human life.

With the development of society and the continuous improvement of human living standards, people's demand for gems is increasing, especially in recent decades, the gem trade has also developed greatly. However, the huge gem trade volume makes natural gems more and more precious and less. In this case, man-made products gradually filled part of the demand of gem trade. At present, as commonly used artificial products materials, there are mainly corundum gems and synthetic cubic zirconia, and glass is a kind of artificial gem, which is mainly used as imitation gems. This paper mainly analyzes the application and development of "gem glass" in artificial products.

First of all, let's look at the application of glass as a material for man-made products. When it comes to glass, many people may think of lamps and utensils. In fact, people have long used glass as "jewelry". Because of the limited production technology, glass is still scarce. At that time, the value of glass was not much different from other gems. With the development of the glass manufacturing industry, the output of glass is increasing, which gradually loses its role as a major factor in the scarcity of precious stones and is more used in daily necessities and utensils.

As a material used in artificial gem, glass has not been paid enough attention. The key is that it is too common and its hardness is not high. The Mohs hardness of synthetic corundum gem is 9, and that of synthetic cubic zirconia is 8.5. Traditionally, people should know that the Mohs hardness of gemstones should be above 7, while the Mohs hardness of glass is 5 ~ 6. Judging from the melting point, gem-like glass has great advantages. Silicon dioxide can only be melted at a high temperature above 1700℃ to make molten crystal glass, which is very expensive. The melting point of the common imitation crystal glass (lead glass) in the market is much lower, usually within 1000℃, and it can be fired in a general small-capacity crucible with a small dosage at a time, but some of its characteristics make it play a great role in the future development. Glass is transparent, corrosion-resistant, heat-resistant and malleable, and its electrical and optical properties make it possible to be used as a gem-like material. Glass has been continuously studied.

Whether people study natural gemstones or artificial products, their research objects are mainly "materials" and "colors". Similarly, the study of glass should also focus on "material" and "color". As far as "material" is concerned, the gem-grade glass we usually use can be special optical glass. The melting temperature of special optical glass is low. If the amount of sodium oxide is increased, the melting temperature can be reduced to the temperature that can be produced by ordinary kiln, and of course the hardness will be reduced (the Mohs hardness of glass produced by ordinary kiln is 5 ~ 6). Glass has a strong plasticity, so as long as its chemical composition is properly adjusted, it can achieve the purpose of imitating gems. The commonly used "lead glass" is to add lead to the glass. After adding lead, the density of glass increased. The greater the density, the slower the light propagates in the glass and the greater the refractive index. Conversely, the smaller the density, the smaller the refractive index. In order to improve the refractive index of ordinary glass, the lead content is generally between 25% and 50%, and some special glasses even contain more than 80% lead, which has a high refractive index. However, the application of lead-containing glass in jewelry has also brought some problems, which is lead poisoning pollution. In addition, "lead" is a metal with low melting point, which is easy to be oxidized. Nowadays, some people process ornaments by inlaying and then electroplating. In the process of electroplating, lead will be oxidized, which will make the surface of jewelry "hazy" and affect the smoothness of jewelry like "mist". In addition, lead is polluted, which makes it banned in some countries. For example, the EU standard is that the lead content is less than one thousandth, so some manufacturers consider removing lead in production. The author thinks that glass can obtain better refractive index without lead by compounding glass materials. In order to meet different needs, there are many brands of optical glass to choose from.

Let's take a look at the importance of "color" for gem materials. The reason why gems are loved by people is that "material" is an indispensable factor, but it is widely accepted by the market and people, and the more important reason is the "color" of gems. Ruby is made of "corundum", which is a very common mineral and can be seen in many places, but only the transparent corundum with medium depth to dark red to purplish red can be called ruby. To confirm whether a ruby is priceless, pigeon blood red or cherry red, besides the same material, the decisive factor is the color of the ruby. Similarly, in man-made products, the study of "color" is more important than that of "material". The author found that there is a very common phenomenon in gem synthesis. The higher the melting point of the material, the greater the hardness, but the less the color, because many colorants can't stand such high temperatures (being volatilized). For example, corundum gems have more colors than diamonds, synthetic cubic zirconia has more colors than corundum gems, and the melting point of glass is much lower than corundum gems and synthetic cubic zirconia, so the advantages in color development are fully reflected. We can make glass of any hue and depth, which can be melted in nature, such as red, yellow, blue, green and purple. Experience tells us that when erbium oxide is added to the glass substrate, the color will become fine pink glass, just like pink tourmaline; After adding neodymium oxide, it will show different colors under different light, which is called "color-changing glass"; Adding "gold trichloride" will present elegant "rose red" gold red glass. Many metal oxides and some other substances can color glass, such as cobalt, copper, iron, nickel, manganese and chromium. Glass has been widely used in the field of artificial products, which is inseparable from its colorful colors. It can be said: "In the field of artificial products, there is no material with more colors and lower price than glass, so the cost performance of glass is self-evident."

Some people think that artificial gem ornaments are likely to be supplied to poor places, but I think the opposite is true. The poorer the place, the more pure gold and pure silver are needed. Where 18K gold jewelry is not necessarily better than pure gold jewelry. Because I am poor, it is not easy to buy an ornament, so I want to buy a value-added product for my children and grandchildren. In cities and towns, people began to look to artificial gem jewelry, because artificial gem jewelry keeps up with the trend, the market, the fashion and the needs of modern youth, so it is getting wider and wider. There is a very common phenomenon abroad: after buying a piece of artificial gem jewelry, you only wear it a few times, mostly for one season to six months. Most of them are bought and worn, and they are worn and lost, because there is no value that can be preserved for generations, mainly based on fashion decoration. With the improvement of people's living standards, it is an indisputable fact that the consumption of ornaments in artificial gem will increase. Before the reform and opening up, gold ornaments were the main products in China. At that time, the consumption of colored natural gemstones was very small, let alone artificial products. ! Probably in the mid-1980s, rare-earth gem glass was popular in the market at that time, but at that time, due to the small market demand and the fact that the production technology and equipment were all produced in small crucibles, the production capacity was not very large. It was in the late 1980s that three kinds of imitation gem glass products (high refractive index rare earth glass, imitation cat's eye glass and imitation Australian jade glass) appeared on the market, and these products did sell well in the jewelry market for a period of time. At first, some people put these imitation gem glasses in gold ornaments. Later, with the gradual increase of manufacturers, the output increased and the price decreased, these imitation gemstone glasses gradually changed to rare gold ornaments (an alloy material).

During the period of 1994, the author shared a booth with a friend from Xinjiang and a friend from Yunnan at the first international jewelry exhibition in Shanghai. On the left are jadeites and gems from Yunnan, and on the right are tourmalines and aquamarine from Xinjiang. The middle author monopolized three kinds of torus: cat's eye glass, high refractive index rare earth glass and Australian jade glass. The result is very interesting. The two counters on both sides are cold and empty, but our counter with imitation gem glass ornaments is always crowded. The key to this situation is that our products are beautiful and the price is low, which makes the author see the great development potential of the colored glass imitation gem market.

When the author visited Wuzhou, Guangxi on 1995, the artificial products in Wuzhou market were mainly corundum gems and synthetic cubic zirconia, and the amount of rare earth glass was also a part, but some glass imitation gem products had some problems in electroplating because of their high lead content. At that time, someone asked if it was possible to produce high refractive index rare earth glass suitable for electroplating. After I went back, I studied it and achieved success. 1996 brought 12 a new colored imitation gem glass product when he went to Wuzhou again. The slogan was "colored glass that can be electroplated", which caused a sensation in the market and achieved certain benefits. However, the output was not large at that time, and the application of imitation gem colored glass was still in its infancy. It was from the late 1990s to the year 2000 that imitation gem glass was really widely used, which was mainly due to the popularity of alloy ornaments and silver ornaments. Many Taiwanese businessmen and foreign-funded enterprises in Wuzhou use these gem-like glass products embedded in alloy ornaments and silver ornaments, pushing the use of gem-like glass to a peak. It can be said that the extensive application of colored glass as artificial gem material in China began in Wuzhou, and developed with the development of Wuzhou gem market.

However, the problems in the glass imitation gem market are also obvious. In just a few years, this product has entered the low-grade competition, which is probably a common problem in the domestic market at present. When that product sells well, it will soon enter vicious competition. For the colored glass that imitates gemstones on the market at present, it is not so much imitation gemstone glass as handicraft glass. As a kind of artificial gem material, the gem-like colored glass used in ornaments has certain requirements and boundaries, and has high requirements on its hardness, refractive index, dialysis degree and texture. To meet high requirements, first of all, the selection of raw materials is very strict, and second, the production process can not be sloppy. Generally, secondary melting in a small crucible can meet the requirements. From these two points of view, high product cost is inevitable. At present, most manufacturers use kiln technology to produce gem-like glass. There is no doubt that the quality is not as good as the gem-like glass produced by a small crucible, and of course the cost will be greatly reduced. In this way, the price competition of low-grade products will suddenly enter a vicious circle.

On the issue of "color", imitation gemstone glass, as its name implies, is glass that imitates the color of natural gemstones, and its color boundary has certain limitations. What kind of red is pigeon blood red? What kind of blue is "Centaurea"? What kind of green is "Colombian Emerald" and other knowledge about the color of gemstones are necessary for learning imitation gemstone glass. But now, ordinary colored glass manufacturers have no energy to study the professional knowledge of these gems. As long as it is red, it is called ruby, as long as it is blue, it is called sapphire, and the green one is called emerald. In order to reduce the cost, simplify the production process as much as possible, and use the cheapest chemical raw materials, which makes the unstable and unstable colored glass production worse; Some people also use the sales slogan "Cheap is the last word", which is understandable from a commercial point of view, but it is not a good idea to do a good job in technology. This is why the color of colored glass imitation gems is becoming more and more unstable. Although the products in the market of imitation gem colored glass are quite chaotic at present, I think imitation gem glass still has its living space. Although it is similar to ordinary stained glass, it is of different grades after all. Those enterprises with scientific research ability, rich professional knowledge and design ability will not waste their efforts on imitation gem glass. It can be said that what kind of natural gemstones are, there will be what kind of imitation gemstone glass, and a number of imitation gemstone glasses different from ordinary colored glasses will definitely reappear in the gemstone market.