The faint brownish to colour at the centre of the fluorite explodes like a supernova when hit with a UV torch! It also has inclusions, possibly pyrite or some other sulphide. But it is the UV response that really makes it pop.
It is likely to be an organic bituminous material causing the brown colour and bright UV response.
Ex Jo Price Collection. Width of view 9mm. Stack of 50 images (white light) and 28 images (UV).
Click on the images below for a higher resolution version.
