Chlorite pellets and residual organic matter in the Mesozoic bedded cherts of Sicily are examined. The pellets are early diagenetic and could be formed in unconsolidated sediments. The conditions in which they were formed may have been determined by decomposition of organic matter. The active surfaces of the organic debris appear to have an essential role in the chlorite nucleation. Further growth might be supported by solid-solution interface phenomena such as the isomorphic substitutions between chemical elements with different charge. The association of chlorite crystal structure polytypes in the same geological unit may be kinetically-related to the variations of the diagenetic conditions. The diagenetic association chamosite-chlorite could also be explained in the same way. Occasional association of chlorite-pyrite in the pellets identifies two stages of diagenesis characterized by different values of oxygen fugacity.

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