Spectacular 5-Color Rock from Franklin, New Jersey, Featuring Esperite, Calcite, Hardystonite, Willemite and Clinohedite

Contributed by: Chris Clemens
minID: YM1-7VQ
Date: Apr 22nd, 2026
Locality: Franklin Mine, Franklin, Sussex County, New Jersey, USA (See on Mindat)
Size: 2.7 x 2.2 x 4.2 inches
Weight: 1.33 lb

Description:
When it comes to fluorescent rocks, the brighter and more colors seen under UV, the better. Franklin, New Jersey, the Fluorescent Mineral Capital of the World, has unquestionably produced some of the brightest and best examples of multi-colored fluorescent rocks found anywhere. This rock is one such example. From the famous Parker Shaft at the Franklin mine, this spectacular rock shows the holy grail of fluorescent colors from this location. Under short wave UV the response is dominated by bright yellow fluorescing esperite, red fluorescent calcite and blue hardystonite. Minor amounts of willemite and clinohedrite provide green and orange, fluorescent accents, respectively.

Originally posted by Chris Clemens on Nature's Rainbows in 2018.