Elusive Multi-Wave UV Fluorescent Hardystonite - Franklin, New Jersey
Contributed by: Chris Clemens
minID: Y9P-864
Date: Apr 28th, 2026
Locality: Franklin Mine, Franklin, Sussex County, New Jersey, USA (See on Mindat)
Size: 6.3 x 4.7 x 9.1 cm
Weight: 481 g
Description:
The beautiful blue, fluorescent mineral hardystonite is a favorite among collectors of specimens from Franklin, New Jersey. This mineral typically shows blue/purple-colored fluorescence under shortwave UV, but little to no response under other wavelengths. In rare cases, hardystonite may also be fluorescent under midwave and longwave UV, and this specimen provides an example of such material. This is a spectacular two-color rock that contains hardystonite and willemite from the Franklin Mine, Franklin, New Jersey. Under shortwave UV the willemite fluoresces bright green and the hardystonite shows a typical deep blue response. Under midwave and longwave UV however, the hardystonite shows a rare pale, lighter blue, fluorescent response, and the willemite glows a more subdued green.
Originally posted by Chris Clemens on Nature's Rainbows in 2017.
Summary of luminescence responses:
Hardystonite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Blue
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Blue
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Blue
- Fluorescence under Longwave (365nm LED) UV light: Green
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Green
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Green