ABSTRACT
Echinoderms have a high-magnesium calcite skeleton whose cristallographie, chemical, and morphological properties make it different from abiotic calcites. The available data show that the single crystal behaviour, the conchoidal fracture properties, the high-magnesium content, and the stereom structure could be partly explained by the properties of the organic macromolecules associated with the mineral phase. Data suggest that these compounds could produce the stereom properties through stereochemical interactions with calcite.
