The light is used for checking fluorescence in diamonds. Diamonds with fluorescence will appear cloudy when viewed with the light on. Fluorescence is not 'diagnostic' but, as with most tests, it eliminates some possibilities, opens other possibilities, suggests which other tests to carry out, and that's how gemologists identify stones.
21mm Jeweler Loupe 10x Magnifier with LED and UV Light
SE Illuminated 10X Magnifying Loupe with LED Light - 21mm Optical Glass Lens, Portable Folding Design, for Jewelry, Geology, Biology - Includes Case and Batteries - Silver Metal Construction : Arts
🔍10X MAGNIFICATION: The Jewelers Loupe features a 10x magnification, allowing for detailed and accurate readings.The minimum scale division of 0.1mm
10x Jewelers Loupe, Illuminated Magnifying Glass, Portable Pocket Reading Magnifier with 25mm with LED Focused Eye Loupe Magnifier for Gems,Coins
Scale Loupe 10x Magnification 8 LED Light 9 Glass Scale Chart Jewelers Eye Loupe Magnifier 25mm Field of View
4Pcs Eye Loupe Magnifier Magnifying Glass, 5X 10X 15X 20X Experimental Monocular Magnifier, Portable Watchmaker Loupe Magnifier Lens Repair Kit Tools for Gems, Coins, Rocks, Stamps : Arts, Crafts & Sewing
Loupe Led - Temu Republic of Korea
Shop 1Pcs 5x/10x/Watch Jewellery Magnifier Loupe Eye Len Eyepiece Repair Kit Tool Portable Jewelers Loupe Magnifying Glass For DIY Jewelry Making
1Pcs 5x/10x/Watch Jewellery Magnifier Loupe Eye Len Eyepiece Repair Kit Tool Portable Jewelers Loupe Magnifying Glass For DIY Jewelry Making Repairing
Package Dimensions: 9.0 L x 2.0 H x 4.0 W (inches) 18mm (0.70) lens size Triplet lens - aplanatic, Achromatic & color corrected Country of Origin
Toyo Professional 10X Magnifying Jeweler's Loupe with 18mm Triplet Lens, Chrome
5x 10x 20x Eye Magnifier Tool Jewelry Watch Magnifying - Temu
4Pcs Eye Loupe Magnifier Magnifying Glass, 5X 10X 15X 20X Experimental Monocular Magnifier, Portable Watchmaker Loupe Magnifier Lens Repair Kit Tools for Gems, Coins, Rocks, Stamps : Arts, Crafts & Sewing