aragonita

Aragonita refers to the mineral aragonite, the orthorhombic polymorph of calcium carbonate (CaCO3). It typically crystallizes in slender needles, tabular or prismatic forms, and may occur as radiating aggregates, fibers, or massive masses. In nature, aragonite is a common inorganic form of calcium carbonate in the skeletons and shells of many marine invertebrates, including mollusks and corals, and it also forms in cave environments as speleothems.

Aragonita occurs in a variety of settings, including marine and freshwater environments, hydrothermal systems, and evaporite deposits. It is frequently associated with biogenic deposits produced by organisms that biomineralize calcium carbonate, as well as with inorganic precipitates in sediments, ooids, and cave formations. Its presence in fossils can help reconstruct past environmental conditions.

In terms of stability, calcite is the thermodynamically stable polymorph of CaCO3 at standard surface conditions, while aragonite is metastable. Over geological timescales, aragonite can transform to calcite through dissolution and re-precipitation or solid-state rearrangement, with the rate influenced by temperature, pressure, and chemical surroundings.

Significance: The isotopic composition of aragonite shells from fossil organisms is a valuable proxy for past ocean temperatures and chemistry, contributing to paleoclimate reconstructions. In modern contexts, aragonite-bearing materials are collected as mineral specimens and occasionally used in decorative applications. The term aragonita is the Spanish-language designation for this mineral.