Crystal structure of of the carbonate mineral aragonite (CaCO3).
Blue: Ca, brown: C, red: O.
The model was produced in the freeware [Vesta](https://jp-minerals.org/vesta/en/), using crystallographic data from de Villiers (1971), downloaded from the [American Mineralogist Crystal Structure Database](http://rruff.geo.arizona.edu/AMS/amcsd.php).