In Zaire (Central Africa), two main kimberlitic fields have been recognized: one at Mbuji Mayi (Kasai province) of Late Cretaceous age and the other on the Kundelungu plateau (Shaba province). At Mbuji Mayi the kimberlite breccia (blueground) contains rounded nodules of what has been called “primary kimberlites”; these nodules show the typical porphyritic texture (two generations of olivine phenocrysts) of many kimberlites; the matrix consists mainly of phyllitic and calcitic material. These rocks may be classified as micaceous kimberlites, contrary to the Kundelungu samples which are mostly of the basaltic type. In both areas, the kimberlites contain the “discrete nodule associations” (Nixon and Boyd, 1973): grains of pyrope, Cr-diopside and magnesian ilmenite. Chemically, they are remarkably similar to the South African, Lesotho and Yakutian rocks. The initial 87 Sr 86 Sr ratios are in the range 0.7040–0.7045 which points to a mantle origin for the kimberlitic magma, with no crustal influence. Rare carbonate inclusions in the kimberlite nodules have the same Sr-isotope composition which suggests a genetic relation between the carbonates (carbonatitic magma?) and the kimberlitic magma. The Cr-diopsides have a 87 Sr 86 Sr ratio of 0.7031 ± 0.0002 which is significantly lower than that of the kimberlites; this implies that these diopsides are more probably xenocrysts from the upper mantle than a crystallizing phase in the kimberlites.