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Zr-rich pyrochlore crystals in carbonatite from San Vicente (Cape Verdes Islands) show cryptic, concentric and rhythmic chemical zonation with Ca increasing and Ti, U and Zr decreasing towards the rims. In one carbonatite, taken from the Camile dyke, previously undocumented cryptic sector zonation of Ti, U and Zr is also observed in these crystals. The chemical variation is investigated by wavelength-dispersive electron microprobe, with both single spot and crystal map analyses. The concentricdoi:10.1180/minmag.1992.056.383.06 fatcat:6nw3vn2o5nbuli6kxuun2l7o4u