top of page

Interesting Zonal Fluorescence in a Barite Crystal from the Linwood mine, Buffalo, Iowa

This specimen of barite from the Linwood mine, Buffalo, Scott County, Iowa, is most interesting from a scientific perspective. It is one of the brightest-fluorescing and phosphorescing barites that I have seen from this location. As a daylight display piece, it doesn’t have much to offer- it’s a drab looking, single, large, grey/yellow colored crystal that was broken off from its matrix, with the plane of breakage showing a perfectly flat cleavage surface. Under UV however, this specimen comes to life, showing bright blue/white fluorescence under all wavelengths, with bright and lasting blue/green phosphorescence after short wave, and green phosphorescence after long wave.

Photographs showing a full view of the barite crystal, showing fluorescent and phosphorescent response under UV, and seen under visible light. Mouse over the scrolling images for wavelength information.

The most interesting aspect of this specimen is the zone within which the fluorescence occurs. Viewing the cleavage surface under UV provides an ideal cross sectional view of the fluorescent region within the crystal, showing that the fluorescence and phosphorescence only occurs in the outer approximately 3 mm of the crystal surface, with the greater interior of the crystal being non-fluorescent. This finding suggests that the solution environment from which this crystal precipitated changed during the final phase of crystallization to include the activator of fluorescence, which was apparently not present during the initial stages of crystal formation. The final result being an outer layer of fluorescent barite deposited over a larger interior of non-fluorescent barite.

View of the basal cleavage surface showing cross sectional view of interior of barite crystal. Photographed under visible and UV light. Note that it is only the outer layer of the crystal that is fluorescent/phosphorescent. Mouse over the scrolling images for wavelength information.

An additional point of interest for this specimen is that it contains a large fluid inclusion within which occurs a mobile gas bubble approximately 6 mm in diameter. As shown in the following photographs, this inclusion can be clearly seen under visible light, and by fluorescence/phosphorescence under UV.

Macro photographs showing the fluid and gas bubble inclusion, taken under visible light and long wave UV. The inclusions do not appear to be fluorescent themselves, but are highlighted the fluorescence/phosphorescence of the surrounding barite. The gas bubble is approximately 6 mm in diameter. Click on the above images for a larger view and wavelength information.

The size of this barite crystal is 8.8 x 5.1 x 4.1 cm, and it weighs 368 grams.

179 views0 comments
bottom of page