• Ultrasonic Cleaning - this is a method used by jewelers to clean jewelry.  The tank or ultrasonic bath is filled with a liquid cleaning solution and employs ultrasonic vibrations which breaks up the dirt/film on the jewelry.

  • Ultra Violet Light - electromagnetic radiation having wavelengths which range from just beyond the violet end of the visible spectrum at roughly 380 nm down to the longest X-ray wavelengths at around 20 nm.  Because of the visible emission peaks in the mercury discharge lamps and low-pressure mercury vapor lamps used to reduce UV light for gem testing, thes lamps are filtered to produce light at 365 nm (LW UV) and 254 nm (SW UV).

  • Unakite - a type of granite rock containing quartz, pink feldspar and green epidote, usually cut in cabochon form or tumbled.

  • Upper Girdle Facets - the triangular facets adjacent to the girdle on the crown (upper portion) of a brilliant-cut stone.

  • Uranium Glass - a yellow glass, also called canary glass, sometimes used as a gemstone simulant.