Pink Aragonite collectibles in a beautiful presentation box, each with a name sticker.

The mineral aragonite is a calcium carbonate with chemical formula CaCO3. It is an unstable polymorph of calcite and is therefore difficult to distinguish from calcite, because most properties are the same. A distinction can be made by means of a colour test: with a Feigl solution, aragonite becomes black, while calcite remains colourless. In addition, aragonite is slightly harder than calcite and a scratch test can be used to determine which mineral it is. A third method of distinction is the habitus: aragonite usually grows in needle-shaped crystals (acicular), while calcite has a leaf-shaped habitus. With the help of powder diffraction, the difference can be clearly determined because aragonite has an orthorhombic structure and not a trigonal one like calcite. Aragonite is always formed at low temperatures close to the earth's surface. Aragonite is found in geysers, hot springs, caves, as oölites in shallow seas, in shells and in pearls. Localities in Europe are Aragon (Spain), Limousis (France), Girgenti (Sicily), Bilin (Bohemia) and Eisenertz (Austria).