Shell with Mercenaria Calite ( #2)

North America Okechobee County, Florida, USA


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Mercenaria permagna is the scientific name (genus and species) for a clam whose fossi lized shells are found in Okechobee County, Florida (among other places). Calcite, a very common mineral, is composed of calcium, carbon, and oxygen as CaC03. So "Mercenaria calcite" is just a mineral collector's name for calcite that has formed inside fossi lized Mercenaria shells. In terms of crystal structure and chemical composition, it is no different from calcite that has formed anywhere else. It is likely that calcite in fossil shells above the sedimentary rock layer containing the Mercenaria shells dissolved in acid groundwater and flowed downward into the Mercenaria shells. The empty cavities of these shells provided ample space for the calcium carbonate to re-precipitate into large, wellformed calcite crystals.