This is a fluorescent youngite specimen from Guernsey, Wyoming. Youngite is an agatized brecciated jasper with a coating of grayish translucent druzy quartz. Found in only one location, the youngite caves near Guernsey, Platte Co., Wyoming. The fluorescent response of youngite under UV is highly variable, with some specimens showing spectacular fluorescence, and others being only dimly fluorescent. This specimen is one of the brighter ones that I've seen. Under SW UV the drusy quartz fluoresces green, and the jasper center fluoresces a blue/grey color with deep blue phosphorescence. The long wave response is more subtle, with the jasper responding a brighter cream/brown and the quartz druse fluorescing darker olive green. The size of this specimen is 12 x 9 x 7 cm, and it weighs 847 grams.
The Youngite caves are located on private property, and have been off-limits to collectors for years.
This speciimen appears to have been trimmed to remove material for lapidary work. This actually has created a very sculptural and aesthetic looking piece. Seen in the above photo under (L to R) visible light, short wave UV (365nm), and long wave UV (365nm).
Same specimen, seen under visible light.
Same specimen seen under short wave UV (254nm).
Same specimen seen under long wave UV (365nm).