Archachatina marginata (Swainson), Achatina achatina (Linnaeus) and Achatina fulica Bowdich were examined for their shell whorl morphometrics (20 snails per species) and the calcium, iron and phosphorus content in the shell whorls (10 snails per species). The species differed in the degree of shell mineralization (the highest in the medium-sized A. achatina, intermediate in the smallest-sized A. fulica and the smallest in the largest-sized A. marginata) which was not age- or environment-dependent, since all the experimental snails were 12 months old adults of 6 whorls, originating from the same snail farm. In all three species the degree of shell mineralization decreased from the apical (oldest) to the body (youngest) whorl, thus depending entirely on the whorl's age. The inter-specific differences in calcium content should be considered when using shells for medical or agricultural purposes.