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Marine biogenic calcification is the production of calcium carbonate by organisms in the global ocean.. Marine biogenic calcification is the biologically mediated process by which marine organisms produce and deposit calcium carbonate minerals to form skeletal structures or hard tissues.
Seashells, namely from bivalves [13] and gastropods, are fundamentally composed of calcium carbonate. In this sense, they have potential to be used as raw material in the production of lime . Along the Gulf Coast of the United States , oyster shells were mixed into cement to make "shellcrete" which could form bricks, blocks and platforms.
The calcium carbonate layers in a shell are generally of two types: an outer, chalk-like prismatic layer and an inner pearly, lamellar or nacreous layer. The layers usually incorporate a substance called conchiolin , often in order to help bind the calcium carbonate crystals together.
The gastropod shell has three major layers secreted by the mantle. The calcareous central layer, ostracum, is typically made of calcium carbonate (CaCO 3) precipitated into an organic matrix known as conchiolin. The outermost layer is the periostracum which is resistant to abrasion and provides most shell coloration.
Shell growth in estuaries is an aspect of marine biology that has attracted a number of scientific research studies. Many groups of marine organisms produce calcified exoskeletons, commonly known as shells, hard calcium carbonate structures which the organisms rely on for various specialized structural and defensive purposes.
The mollusc shell is a biogenic composite material that has been the subject of much interest in materials science because of its unusual properties and its model character for biomineralization. Molluscan shells consist of 95–99% calcium carbonate by weight, while an organic component makes up the remaining 1–5%.
Nacre is composed of hexagonal platelets, called tablets, of aragonite (a form of calcium carbonate) 10–20 μm wide and 0.5 μm thick arranged in a continuous parallel lamina. [2] Depending on the species, the shape of the tablets differs; in Pinna, the tablets are rectangular, with symmetric sectors more or less soluble.
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. Aragonite crystal structure