Selenite and Chalcedony, Hay Springs, Nebraska
Contributed by: Chris Clemens
minID: E3K-V7U
Date: Apr 15th, 2026
Locality: Hay Springs, Sheridan County, Nebraska, USA (See on Mindat)
Size: 8.6 x 5.1 x 15.6 cm
Weight: 670 g
Description:
This unusual fluorescent specimen consists of crystals of honey-brown selenite sandwiched between two layers of light grey chalcedony. This specimen is brightly fluorescent under midwave UV, but only shows a weak response under shortwave and longwave UV. This specimen was collected around Hay Springs, Sheridan County, in northwest Nebraska.
The first photograph shows fluorescence under midwave UV (302 nm). The selenite fluoresces a burnt orange color and the surrounding layers of chalcedony fluoresce bright green. The green fluorescence of the chalcedony layers is activated by trace amounts of uranium (in the form of the uranyl ion).
Under visible light above, honey-brown crystals of selenite are seen sandwiched between two layers of light grey chalcedony.
Originally posted by Chris Clemens on Nature's Rainbows in 2024.
Summary of luminescence responses:
Chalcedony (Mindat) (RRUFF)
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Green
- Fluorescence under Midwave (305nm Lamp/Mercury) UV light: Orange