Daylight Fluorescent Hyalite Opal, Zacatecas, Mexico
Contributed by: Chris Clemens
minID: FN6-UXY
Date: Apr 21st, 2026
Locality: Zacatecas, Mexico (See on Mindat)
Size: 6.71 x 3.81 x 10.1 cm
Weight: 165 g
Description:
Colorless to greenish, transparent, glassy bubbles of hyalite opal (Opal-AN) covering an unknown brown/grey colored matrix, from Electric Opal Knob, Zacatecas, Mexico. The hyalite opal shows a bright green, fluorescent response under both SW and LW UV, and exhibits yellow/green daylight fluorescence. The green, fluorescent response seen in this material is due to trace amounts of uranium included in the opal silica. Due to the uranium content, this specimen is moderately radioactive and was measured at 200-300 cpm at 1 cm.
The Electric Opal Claim in Zacatecas, Mexico produced specimens of hyalite opal that were notable for having brilliant green fluorescence under UV, and bright green daylight fluorescence when viewed under shaded daylight outside. The Electric Opal Claim produced many high-quality specimens of this material between 2013 and 2018, but due to the limited size of the opal-bearing layer, has been subsequently mined out.
Originally posted by Chris Clemens on Nature's Rainbows in 2019.
Summary of luminescence responses:
Opal-AN (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Green
- Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Green
- Fluorescence under Daylight: Green