Green Fluorescent Fluorite, Fourmile Creek, Colorado
Contributed by: Chris Clemens
minID: E92-Y85
Date: May 21st, 2026
Locality: Fourmile Creek Area, Fremont County, Colorado, USA (See on Mindat)
Size: 38 x 27 x 65 mm
Weight: 74 g
Description:
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 site has produced some of the finest US examples, but never in large quantities. The green fluorescence has been speculated to be caused by uranyl activation (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.
Originally posted by Chris Clemens on Nature's Rainbows in 2020.
Summary of luminescence responses:
Fluorite (Mindat) (RRUFF)
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Green