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Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (Ca CO 3), the others being calcite and vaterite.It is formed by biological and physical processes, including precipitation from marine and freshwater environments.
The thermodynamically stable form of CaCO 3 under normal conditions is hexagonal β-CaCO 3 (the mineral calcite). Other forms can be prepared, the denser (2.83 g/cm 3) orthorhombic λ-CaCO 3 (the mineral aragonite) and hexagonal μ-CaCO 3, occurring as the mineral vaterite. The aragonite form can be prepared by precipitation at temperatures ...
A range of biochemical calcification (biocalcification) mechanisms exist, indicated by the fact that marine calcifiers use different forms of calcium carbonate minerals. Within this range of mechanisms, there are two broad categories of biogenic calcification in marine organisms: extracellular mineralization and intracellular mineralization.
Test shape is highly variable among different foraminifera; they may be single-chambered (unilocular) or multi-chambered (multilocular). In multilocular forms, new chambers are added as the organism grows. A wide variety of test morphologies is found in both unilocular and multilocular forms, including spiraled, serial, and milioline, among others.
Limestone is the most common carbonate rock [3] and is a sedimentary rock made of calcium carbonate with two main polymorphs: calcite and aragonite. While the chemical composition of these two minerals is the same, their physical properties differ significantly due to their different crystalline form. The most common form found in the seafloor ...
Forsterite. In chemistry, isomorphism has meanings both at the level of crystallography and at a molecular level. In crystallography, crystals are isomorphous if they have identical symmetry and if the atomic positions can be described with a set of parameters (unit cell dimensions and fractional coordinates) whose numerical values differ only slightly.
CaCO 3 (s) + H 2 O + CO 2 (aq) → Ca 2+ (aq) + 2HCO − 3 (aq) If the amount of dissolved carbon dioxide drops, the reaction reverses to precipitate calcite. As a result, calcite can be either dissolved by groundwater or precipitated by groundwater, depending on such factors as the water temperature, pH, and dissolved ion concentrations. When ...
Phase transitions (phase changes) that help describe polymorphism include polymorphic transitions as well as melting and vaporization transitions. According to IUPAC, a polymorphic transition is "A reversible transition of a solid crystalline phase at a certain temperature and pressure (the inversion point) to another phase of the same chemical composition with a different crystal structure."