Liebigite from Colorado
Contributed by: Michael Crawford
Date: Jun 29th, 2025
Locality: Schwartzwalder Mine (Ralston Creek Mine), Ralston Buttes Mining District, Jefferson County, Colorado, USA (See on Mindat)
Size: 6 x 11 cm
Description:
This is a specimen of liebigite (Ca2(UO2)(CO3)3 · 11H2O) from the Schwartzwalder Mine, Jefferson County, Colorado. The liebigite occurs as a yellow coating on a fracture surface. The specimen fluoresces blue green under all wavelengths of UV light. The blue-green fluorescence is like other uranyl-carbonate minerals activated by the linear uranyl ion. They all have vibronic spectral peaks that are shifted to shorter wavelengths compared to the uranium minerals like autunite that fluoresce yellow-green (see spectral plots).
These are some other uranyl-carbonate minerals with blue-green fluorescence.
Schrockingerite (NaCa3(UO2)(CO3)3(SO4)F · 10H2O)
Bayleyite (Mg2(UO2)(CO3)3 · 18H2O)
Andersonite (Na2Ca(UO2)(CO3)3 · 6H2O)
The emission spectra of these minerals show that wavelengths of the vibronic peaks are slightly different from one another. The shifts are caused by differences in coordination between different cations, anions, and the uranyl ion in each mineral. Emission spectra have the potential to assist in the identification of uranium minerals.
The specimen’s radioactivity is around 900 CPM.
Summary of luminescence responses:
Liebigite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Green
- Fluorescence under Midwave (305nm LED) UV light: Green
- Fluorescence under Shortwave (255nm LED) UV light: Green