Dr. Yuan talks about diamonds: heat treatment of red sapphire diamonds
Release time:
2022-02-02 00:00
Most of the natural red sapphire after heat treatment, the internal original composition after simple heating to make the composition of the change, and make the color change.
Different effects can be obtained due to the different redox environments during the heat treatment. In an oxidizing environment, Fe can be2-Become Fe3-It is known that high-priced iron does not participate in the formation of blue, so it can make the color of sapphire lighter. For example, many Australian dark blue sapphires are processed to obtain a more satisfactory blue color at a processing temperature of 1600 to 1900°C. Conversely, heating in a reducing environment can make Fe3-Reduction to Fe2-Then the blue deepened. A milk-colored corundum geude is obtained by this treatment at a temperature of about 1600°C.
Heat treatment can also improve the color of ruby, such as eliminating the purple tone of ruby and the color spots of sapphire, deepening the color of colorless or light-colored sapphire, and heat treatment can also be used to eliminate the silk luster of ruby or sapphire or enhance the starlight phenomenon of starry ruby and sapphire. The treatment of only heating is generally accepted, has no effect on the durability of the gem, and does not require special maintenance. The color of red sapphire has been significantly improved, and the change is large. At the same time, the internal inclusion body is affected by high temperature, melting phenomenon occurs, the visible degree is reduced, and the clarity and transparency are improved.
The international red and blue gemstone community is only heat-treated without adding other substances. The original substances in gemstones are used to produce excellent changes during heat treatment and are stable. This optimization is acceptable.
Cultivated diamonds are diamonds grown under artificial environment. In particular, CVD cultivated diamonds grow under negative pressure. When the growth speed is fast, the color will produce brown due to plastic deformation. The use of high temperature and high pressure or low pressure and high temperature treatment will reduce or eliminate brown. The obtained colors are divided into two categories: gray black and positive white. The gray-black color is caused by the machine and the growth process. These two reasons are fundamentally solved when growing, and positive white can be obtained.
Cultivated diamonds are artificially grown, and a simple heat treatment is added, so that the obtained positive white is a long-term stable synthetic diamond, which is still sold in the name of laboratory-grown diamonds, which is reasonable and justifiable. Whether the cultivated diamond has undergone post-heat treatment, especially slight heat treatment, cannot or is not easy to identify. The grading report cannot clearly determine whether it has undergone heat treatment. In recent years, the unclear marks in the remarks column on the certificate regarding post-heat treatment, such as "may include post-growth treatment" and "no sign of post-growth treatment" are unnecessary.
For the problem of gray and black, white and gray series of colored stones can be established and rated by color series. The reason for the gray-black after the color change will be found out in the near future, so that the problem of CVD cultivating diamond gray-black can be completely solved.
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Dr. Yuan Zhizhong, Chairman of Bench Diamond Technology, gave a lecture entitled "Identification of Gem Diamonds Cultivated by CVD Method" at the Appraisal Institute on the 11.9 at the invitation of the Appraisal Institute of Taiwan Gemological Institute. In the lecture, Yuan Dong introduced in detail the historical principles of CVD diamonds and their development status, and introduced in detail several methods to distinguish CVD diamonds from natural diamonds on how to identify gem-grade CVD diamonds that participants are concerned about! Yuan Dong's wonderful speech was well received by the participants!
Yuan Dong Attends the Symposium at the Invitation of Hangzhou Jewelry City
Dr. Yuan Zhizhong, Chairman of Bench Diamond Technology, was invited by Hangzhou International Jewelry City to attend an academic symposium on November 19, 2013. At the symposium, Yuan Dong gave a speech entitled "International Situation and Identification of CVD Synthetic Diamonds" on the current situation of CVD synthetic diamonds that jewelers are concerned about and how to distinguish CVD diamonds from natural diamonds. In the speech, Yuan Dong introduced in detail the history of CVD diamonds, the international situation of CVD diamonds and the commonly used identification methods of CVD diamonds, and answered some questions raised by jewelers. Mr. Yuen's speech was well received by the participants, and all jewelers said they benefited.
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