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UV lamp is an important auxiliary identification instrument. It is mainly used to observe the luminescence of gemstones, and the fluorescence characteristics of gemstones under long and short wave ultraviolet light can help identify gemstones.

Working principle   

UV lamp tubes can emit ultraviolet light waves within a certain wavelength range. After passing through a specially designed filter, only ultraviolet light with a main wavelength of 365nm or 253.7nm is emitted. While different wavelengths of ultraviolet light shining on gemstones,it can emit fluorescence of different colors and brightness.It can help identify gemstones based on their characteristics.

Types and characteristics of gemstone ultraviolet lamps

The ultraviolet lamps used for jewelry identification are mainly divided into two categories: dark box ultraviolet fluorescent lamps (Figure 1) and ultraviolet fluorescent flashlights (Figure 2).

Figure 1 dark box ultraviolet fluorescent lamps

Figure 2  ultraviolet fluorescent flashlights

Operation steps

1. Clean the gemstones, place them in the dark box, and then close the dark box;
2. Turn on the switch, press the long wave (LW) or short wave (SW) buttons respectively, and observe the luminescence of the gemstone with your eyes close to the fluorescent lamp eyepiece;
3. Record the observed luminescence phenomenon of gemstones;
4. Turn off the UV light and continue to observe. If the gemstone still emits light, it indicates that the gemstone has phosphorescence and should also be recorded;
5. Take outthe gemstone and turn off the UV fluorescent lamp.

Precautions

1. UV light is harmful to the eyes. Remember not to look directly at the UV lamp. When operating, place the sample first and then turn on the switch.
2. Use tweezers to put the gemstone into the box for operation to prevent UV light damage to the skin.
3. Dye and fill gemstones, paying attention to the fluorescence of the filling area.
4. The reflection of light on the surface can easily be mistaken for fluorescence
5. There may be significant differences in fluorescence between samples of similar gemstones.
6. The fluorescence of transparent samples is different from that of opaque samples.
7. It is only an auxiliary means and requires comprehensive judgmentwith other

Main uses

 Assist in identifying gemstone varieties
Different gemstones have different fluorescence characteristics, which can distinguish different gemstone varieties. Like ruby – garnet, ruby has red fluorescence, while red garnet has no fluorescence, indicating fluorescence inertness; Sapphire – Benitoite, Blue sapphire often lacks fluorescence under shortwave ultraviolet light, while Benitoite can exhibit strong blue white fluorescence.
Help distinguish diamonds and diamonds imitations
The fluorescence color and intensity of diamonds under ultraviolet light vary greatly, from none to strong, with various colors visible (Figure 3). However, most of their imitations only have a single fluorescence color. Therefore, ultraviolet light is very useful for identifying group set diamonds and bulk loose diamonds. If they are all diamond stones, their fluorescence will not be uniform, while imitations have a more uniform fluorescence.

               Figure 3 Fluorescence performance of various diamonds

Help distinguish between synthetic and natural gemstones
Natural sapphires generally do not exhibit fluorescence under short wave ultraviolet light, while synthetic sapphires exhibit a unique milky white fluorescence. Most synthetic emeralds emit bright red fluorescence under long wave ultraviolet light, which is significantly different from natural emeralds.
Help identify manually optimized gemstones
Natural jadeite generally has no fluorescence or weak fluorescence under UV light, while some jadeite (“B-grade”) that has been bleached and filled will show obvious fluorescence under UV light (Figure 4).

  
Figure 4 Comparison of natural light and ultraviolet fluorescence of different jadeite
(The above image is under natural light, and the following image is under long wavelength ultraviolet light)