Aragonite is a carbonate mineral.

It has interesting habits. It has exactly the same chemical make-up as calcite. It is thus a polymorph of calcite. The most interesting crystals, cyclic twins, occur in Spain and Morocco. Corals and some sea creatures secrete aragonite for their shells. It is also found around hot springs and in caves.

Aragonite is the less common and stable of the two, calcium carbonate minerals; the other is calcite. Occurring in near-surface deposits, aragonite forms crystals that are glassy-white, slender, and tapering, as well as columnar masses, stalactites, and crusts. Some specimens fluoresce green (see fluorescence).

Aragonite is formed through organic agencies as pearl and mother-of-pearl; it is precipitated as a hot-spring deposit and in beds with gypsum as an evaporate deposit.

The name comes from the province in Spain, Aragon where it was first noted.