This is a must have to help determine some synthetic gemstones using their reaction to Short Wave UV.

The OEM Mini S10 SW 254nm Far UV Ultraviolet Light Flashlight is designed for specialized use with fluorescent minerals and gemstones. Featuring a Korea UV-C LED chip, it emits a shortwave 254nm wavelength, housed in a durable aluminium alloy body with a ZWB3 black filter. Compact at 11.80cm x 2.40cm and lightweight at 76g, it operates on a rechargeable 3.7V Li-ion 18650 battery with a radiation power of 90mw.