A wonderful example of Cave-in-Rock fluorescence. Regular Eu2+ purple fluorescing fluorite with another generation of petroleum included fluorite. Interestingly the petroleum has given the fluorite a very dark purple color, almost to the point of looking black. It is only under direct light that you can see the shades of purple on this face, including the petroleum included one.
Locale: Cave-in-Rock, Illinois, USA
Weight: 4lb 2oz | 1871g
Dimensions: 6.0 x 4.0 x 3.5 in | 153 x 102 x 88 mm
However, on the underside of this specimen we see clear and gemmy massive fluorite. This side doesn't has almost no fluorescent inclusions and thus has a much lighter color compared to the front face. Also on this face are a lot of well formed and lustrous garnets.