Calcium carbonate structure in mollusc shells can be determined by infrared spectroscopy. Infrared analysis is easier and less expensive than most other current methods for macroscopic analysis of the structures in gross calcium carbonate. Shell specimens from 22 river species were shown to be entirely aragonite; the composition of two shells of Strombus gigas Linnaeus was primarily aragonite with a thin surface layer of calcite and that of a fossil oyster shell (Ostrea sp.) was entirely calcite.
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Compere et al. (1973) studied this question.