Few color changes of diamonds are caused by ultraviolet light and visible fluorescence. The famous 56.07ct Tavernier diamond studied by the author is the only diamond with color change caused by ultraviolet and short-wave visible fluorescence. Tavigne of France is as famous in western countries as Kyle Polo of Italy. Kyle Poirot traveled and lived in China, bringing back a great deal of jewelry, spices and technical knowledge from China to Italy, and introducing China to western countries in the form of travel notes. In the17th century, the French travel explorer Tavernie visited India many times, wrote his travels and adventures in a book, and introduced India to the west. The most impressive thing about Tabini's travel and exploration in India is that he brought back many rare and precious diamonds from India, and this 56.07-carat "Tabini" diamond may be one of them. Because the color of this "Tavinine" diamond is brown, it has not aroused widespread interest in the past.

This 56.07-carat "Tavinier" diamond is brown under incandescent lamp and turns brown and pink in the sun, and the color change is quite obvious. Because the spectral transmittance curve of this diamond is a typical brown diamond spectrum in the visible light range, the spectral transmittance gradually increases with the increase of wavelength, and it does not have the typical bimodal or multimodal curve characteristics of Alexander effect at all, so it can be concluded that the color change of this diamond is different from Alexander effect.

This "Tavinine" diamond will emit strong blue fluorescence under near ultraviolet radiation. The author measured the transmission spectrum of this diamond under the irradiation of incandescent lamp and D 65 sunlight simulation light source by using the experimental spectrum system specially for measuring the color of gemstone. It turns out that this diamond will emit strong blue fluorescence under the excitation of sunlight. It is the blue fluorescence excited by sunlight that makes the color of this diamond change obviously, which also explains the real reason for the discoloration of this "Tavinine" diamond.

Fig. 3- 16 shows the visible-light excited fluorescence spectrum of "pub" diamond indirectly measured at room temperature, and draws the fluorescence spectrum of N 3 color phonons for comparison. At room temperature, due to the intense thermal vibration of atoms, the fluorescence radiation of N3 color center has no line spectrum and radiation peak, and becomes a continuous radiation spectrum. The intensity distribution of the measured visible-light excited fluorescence emission spectrum is basically consistent with the average value of the theoretically calculated N3 color center fluorescence emission spectrum, and the wavelength range of the spectrum is consistent, which indirectly proves that the visible-light excited fluorescence of "Tavinine" diamond is radiated by N 3 color center. Figure 3- 17 shows the transmission spectra of "pub" diamonds under the simulated solar light source of incandescent lamp and xenon lamp respectively. The transmission spectrum of "Tavinier" diamond under incandescent lamp is similar to that of type IA brown diamond. The transmission spectrum under sunlight overlaps with the fluorescence radiation of N3 color center in the short wave range, which leads to discoloration.

This Tavinine diamond is Iaa.

Fig. 3-16 fluorescence spectrum of "tavinine" diamond

At room temperature, the ultraviolet fluorescence spectrum of N3 color center is continuous and has no characteristic radiation peak. The dotted line indicates the fluorescence spectrum distribution of N3 color center; The fluorescence spectrum of "Tavinine" diamond is consistent with the average value of N3 color center calculated theoretically, and the wavelength range is consistent, which indirectly proves that blue fluorescence is produced by N3 color center.

Fig. 3- 17 transmission spectrum of "Tabini" diamond

1- transmission spectrum under incandescent lamp;

2-Xenon lamp simulates the transmission spectrum in sunlight, which is the superposition of the transmission spectrum under incandescent lamp and the fluorescence radiation of N 3 color center. "Tavernier" diamond is brown under incandescent lamp and reddish brown and pink under the sun.