vateriittis

Vateriittis is a mineral polymorph of calcium carbonate, meaning it shares the same chemical formula (CaCO3) as other forms like calcite and aragonite but possesses a different crystal structure. It is the least stable of these common polymorphs under standard surface conditions. Vateriittis typically forms as tiny, microscopic crystals. Its appearance can vary, often described as white to yellowish or grayish. The crystal habit is generally acicular or prismatic, though it can also occur in spheroidal aggregates.

Vateriittis is often found associated with calcite and aragonite in sedimentary rocks, especially limestones and marbles. It can also form in biogenic environments, such as in the shells and skeletons of certain marine organisms, though it is less common than aragonite or calcite in these structures. The formation of vateriittis is favored by specific conditions, often involving rapid precipitation from aqueous solutions, particularly those with higher magnesium content or under specific temperature and pH ranges. Due to its instability, vateriittis readily transforms into calcite over geological timescales, especially in the presence of water. This transformation is a key factor in its relative rarity in ancient geological formations. Its presence can sometimes be an indicator of recent precipitation or specific diagenetic processes.