Check the listing for details. Fluorescent Willemite on Slickenside *Sterling Mine, New Jersey*. Condition: Used. Listed at 20.00 USD. Longwave and shortwave fluorescent Willemite on a Franklinite slickenside. Fluorescent minerals use either a Shortwave, Midwave, or Longwave Ultraviolet light. These are NOT black lights. Location: Sterling Mine, Ogdensburg, New Jersey.