Yellow Fluorite with Ozonide Activated Fluorescence – Aouli, Morocco

Contributed by: Michael Crawford
Date: Oct 6th, 2026
Locality: Aouli, Mibladen, Aït Oufella Caïdat, Midelt Cercle, Midelt Province, Drâa-Tafilalet Region, Morocco (See on Mindat)
Size: 5.5 x 8 cm

Description:
This yellow fluorite specimen is reportedly from Aouli in Morocco’s Midelt Province. Yellow fluorite occurs in lead-zinc veins near Aouli, where mines operated from 1926 to 1975. However, the mines yielded few specimens while they were in production, and there has been minimal specimen recovery from Aouli for decades. Yellow fluorite labeled "Aouli" are more likely from Sidi Ayed, an area of more vein deposits that is 8.5 km NNW of Aouli. A third area of vein deposits with yellow fluorite, Sidi Said, lies 15 km WSW of Aouli. (see https://www.mindat.org/mesg-252684.html)

Hydrothermal veins at Aouli, Sidi Ayed, and Sidi Said are hosted in Paleozoic schists and granites. Rifting during the Upper Triassic-Early Liassic period, allowed the development of vein structures along NNE-SSW to E-W trending normal faults and tension gashes, as well as WNW-ESE trending normal faults with a strike-slip component (Yaagoub and others, 2021). The veins are up to 40 meters in thickness and 13 km in length.

Under longwave UV light, the fluorite cubes show distinct zoning: pink-fluorescent outer zones surround violet-blue cores. Under shortwave UV, the zoning remains, but the outer zones fluoresce bright pale yellow and the cores appear dimmer pale yellow. Bill (1982) explained that ozonide incorporated into the fluorite lattice produces the yellow color of fluorite from Germany. Although Bill did not address their fluorescence, ozonide and europium produce the pink longwave emission. Ozonide and other activators produce yellowish-white shortwave emissions. The yellow color and fluorescent response of this Moroccan fluorite is the same as German yellow fluorite. Europium substituting for calcium causes the violet-blue longwave fluorescence of the cores.

The longwave emission spectrum of the pink outer zone contains a 422 nm peak from europium replacing calcium and broad peaks near 574 and 604 nm from a second activator. The 574–604 nm orange emission may arise from ozonide combined with a lattice defect. Together with the 422 nm violet-blue emission, it produces the observed pink color. The violet-blue core has a single longwave peak at 422 nm, activated by europium.

The shortwave spectrum is noisy but shows sharp ultraviolet peaks at 320 and 336 nm, characteristic of cerium (Ce³⁺) substituting for calcium. It also contains several visible region peaks whose causes remain unknown; possible contributors include ozonide, other elements, and lattice defects.

The specimen measures 8 × 5.5 cm, and its largest fluorite cube is 1.5 cm across.

REFERENCES:
Bill, H., 1982, Origin of the coloration of yellow fluorites: The O3? center structure and dynamical aspects, J. Chem. Phys., V.76, pp.219–224

Yaagoub, D., Hinaje, S., El Fartati, M., Gharmane, Y., Ouhssaine, A., 2021, Role of Triassic tectonics in the emplacement and distribution of hydrothermal mineralizations in the Aouli mining district (Upper Moulouya, Morocco): Journal of Iberian Geology, v.47, pp. 577-597