Analytical SEM observations show that the inorganic fraction of interstitial matrix and coatings of pyrite framboids consists only of A1 and Si compounds. XRD patterns from bulk concentrates of the pyrite reveal the presence of both kaolinite and quartz in this fraction from marine and nonmarine mud rocks and, dominantly, quartz with little or no kaolinite from coal. These minerals are inferred to be present within framboidal interstices and coatings and can be alternate to or in association with organic matter in these positions. The strata are of Westphalian-C age at the Gastrioceras listeri marine horizon, near Sheffield, England. The mineral and organic material are regarded as early diagenetic, the kaolinite and quartz being syndepositional with the pyrite: the organic component may be of this age or later, probably having undergone some subsequent maturation.

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