Aragonite - Wikipedia
Aragonite is thermodynamically unstable at standard temperature and pressure, and tends to alter to calcite on scales of 10 7 to 10 8 years. The mineral vaterite, also known as μ-CaCO 3, is another phase of calcium carbonate that is metastable at ambient conditions typical of Earth's surface, and decomposes even more readily than aragonite.
- Crystal class: Dipyramidal (mmm), H-M symbol: (2/m .[PDF]GET PRICE >>