Barite over Fluorite
Cave-in-Rock District
Hardin County, Illinois
20 cm x 12.7 cm x 12.5 cm, 4.10 lbs / 1.86 kg
Here is a very unusual Illinois fluorite specimen out of my personal collection.
It is believed to be from the Annabel Lee Mine, but I cannot verify this since the old label was long gone.
Based on the coloring of the exposed fluorite on the edges and back side and the form of the overlying barite, it very likely came from the Annabel Lee Mine.
This is a large cluster of fluorite that is almost completely covered
in micro bladed barite crystals on the front side.
The large central fluorite cube measures 7.6 cm across.
Another thing I love about this specimen is if you look on the left side of the specimen,
there is a cleaved fluorite covered in the barite, showing cleaves can, in fact, be ancient.
There is also a sprinkling of what I assume are micro pyrite crystals on top of the barite.
However, I don't believe I have seen spherical pyrite before, such as these.
The specimen has a very odd and interesting fluorescence.
The barite fluoresces white under UV lighting.
Holding the UV light close to the barite, the fluorescence looks a pale yellow.
Removing the UV light shows some phosphorescence, as the yellow slowly dims.
It would appear that this phosphorescence is from the fluorite under the barite.
At the right edge of the specimen is a small area
where the barite is missing from the edge of a fluorite cube.
The exposed fluorite make it possible to see that the yellow fluorescence is not merely a coating on the fluorite, but actually extends several millimeters down into the crystals.
On the back side of the specimen, there is also some barite, but nothing like the front side as it is mostly contacted on the back.
The fluorite fluoresces purple, except at the top layer where the petroleum is layered.
A large and quite unique specimen for sure.
