Bayleyite and Schrockingerite from Ambrosia Lake, New Mexico
Contributed by: Michael Crawford
minID: 2FJ-WJH
Date: Jun 29th, 2025
Locality: Ambrosia Lake Mining Sub-district, McKinley County, New Mexico, USA (See on Mindat)
Size: 6 x 4 x 19 cm
Description:
This specimen contains two fluorescent uranium bearing minerals, yellow bayleyite (Mg2(UO2)(CO3)3 · 18H2O) and greenish grey schrockingerite (NaCa3(UO2)(CO3)3(SO4)F · 10H2O) that were deposited on a dark sandstone surface. Most of the surface is covered by yellow bayleyite and schrockingerite occurs along the top edge and right tip of the specimen. The specimen comes from the Ambrosia Lake Mining Sub-District, McKinley County, New Mexico.
Both minerals fluoresce blue-green under all wavelengths of UV light. The fluorescence is activated by the uranyl ion in each mineral’s crystalline structure. The shortwave emission spectra show the characteristic vibronic signature created by uranyl activation. The peak positions of the spectra are different for the two minerals because the uranyl ion is coordinated with different cations and anions in the two minerals.
The mindat.org description of this specimen speculated that the greenish grey mineral was schrockingerite. The emission spectrum matches a schrockingerite spectrum from a Wyoming specimen. This match illustrates the potential of emission spectra to aid in the identification of uranium bearing minerals.
The radioactivity of the bayleyite is 3000 CPM to 3400 CPM.
Summary of luminescence responses:
Bayleyite (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
- Fluorescence under Longwave (365nm LED) UV light: Green
- Fluorescence under Midwave (305nm LED) UV light: Green
- Fluorescence under Shortwave (255nm LED) UV light: Green