Uranocircite from Germany
Contributed by: Michael Crawford
Date: Jun 18th, 2026
Locality: Streuberg Quarry, Bergen, Vogtlandkreis, Saxony, Germany (See on Mindat)
Size: 35 x 35 mm
Description:
This is a specimen of uranocircite crystals (Ba(UO2)2(PO4) 2 · 10H2O) on a granite matrix from the Streuberg Quarry, Bergen, Saxony, Germany. The Streuberg Quarry is the type locality for uranocircite. Uranocircite is a secondary mineral formed along fractures within the granite. It forms thin tetragonal, translucent, greenish yellow tabular crystals in clusters with fan-like sub-radial aggregates.
This uranocircite fluoresces bright green under all wavelengths of UV illumination. The green fluorescence is intrinsic and is activated by the uranyl ion in uranocircite's chemical structure. The vibration of the uranyl ion when excited by UV light emits a spectrum with four sharp peaks at 503 nm, 524 nm, 547 nm, and 572 nm. The highest peak is at 524 nm. The position of these vibronic peaks of uranocircite and the number of peaks differ from other uranium minerals because different elements in coordination with the uranyl ion modify its vibration.
The radioactivity of this specimen is around 1400 cpm. It is high because the uranyl ion is part of the mineral structure and not an impurity in a mineral.
Summary of luminescence responses:
Uranocircite (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