This unusual large "shard" of a deep purple-blue Fluorite crystal is full of disseminated petroleum inclusions from the Annabel Lee Mine in the Illinois Fluorspar District. This really interesting piece from the famous Ross Lillie collection is one of the largest and best examples of its kind we're aware of! This thin Fluorite crystal measures over three and a half inches at its longest edge and there is a second crystal in parallel growth on one corner, and it is highly translucent especially when backlit. Both crystals exhibit stepped growth with notches along their edges, distinctive of some of the larger Fluorite specimens from here. When backlit, the Fluorite shows variegated color on the interior from blue, to purple-blue to a faint yellowish and there is a deep purple rim along two of the edges. The brownish petroleum inclusions are also very obvious with backlighting and are 1 to 2 mm in size and there is also a criss-crossing pattern of them too that may be following crystallographic/cleavage traces internally. Ex. Ross Lillie collection (RCL0689) with label.