These references may be of interest:
Parnell, J., 1983 The distribution of hydrocarbon minerals in the Welsh Borderlands and adjacent areas. Geological Journal, 18, 129-139.
Parnell, J., 1988 Mineralogy of uraniferous hydrocarbons in Carboniferous-hosted mineral deposits, Great Britain. Uranium, 4, 197-218.
Eakin, P.A. & Gize, A.P., 1992 Reflected-light microscopy of uraniferous bitumens. Mineralogical Magazine, 56, 85-99.