Rare green fluorescent botryoidal fluorite from the Fourmile Creek area, near Canon City, Fremont County, Colorado. Fluorite in botryoidal form is rare and the Canon City has produced some of the finest US examples, but never in large quantities. The green fluorescence has been speculated to be caused by uranyl acitvation (Robbins M. Fluorescence, Gems and Minerals Under Ultraviolet Light. 1994). This specimen is radioactive (approx. 200 cpm at 1 cm), providing evidence in favor of the proposed uranyl-activated mechanism of fluorescence. The size of this piece is 65 x 38 x 27 mm.
Green fluorescence is seen under short wave UV (254 nm).
Dimmer olive-colored fluorescence is seen under long wave UV (365 nm).
Under visible light, the Fourmile Creek fluorite has a dusty grey/purple coloration.