The features characteristic of competitive growth such as plane intercrystalline boundaries, and increasing crystal size away from the substrate, together with the high frequency of enfacial junctions are regarded by others as intrinsic to cements and form the mainstay of its identification. The features of competitive growth are based on published crystal growth diagrams which are unrealistic because of gross over-simplification. The high frequency of enfacial junctions, claimed as the least unequivocal criterion for cement recognition, still requires explanation. The jerky growth required by cessation of one crystal's face while others grow against it seems unnatural.

Three new diagrams for specific calcite crystallographic forms ( (1011) , (4041) , and (0112) rhombohedra) are introduced. These show competitive or impingement aggregates developed through 3 or 4 maturation stages, and occuring in two basic types, one in which the crystals develop positive elongation, and the other in which negative elongation develops. These graphic models find their closest natural analog in parallel-side veins, but their properties can be applied to pore-fill cements which grew by seeding (without epitaxy) onto the pore walls.

The apparent enigma between the absence of enfacial junctions in the new diagrams and the high recorded frequency in natural aggregates is explained by reference to selected examples.

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