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  2. Calcium - Wikipedia

    en.wikipedia.org/wiki/Calcium

    Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust, and ...

  3. Apatite - Wikipedia

    en.wikipedia.org/wiki/Apatite

    Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH −, F − and Cl − ion, respectively, in the crystal. The formula of the admixture of the three most common endmembers is written as Ca 10 (PO 4) 6 (OH,F,Cl) 2, and the crystal unit cell formulae of the individual ...

  4. Limestone - Wikipedia

    en.wikipedia.org/wiki/Limestone

    Calcium carbonate: inorganic crystalline calcite or organic calcareous material. Limestone (calcium carbonate CaCO3) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO3. Limestone forms when these minerals ...

  5. Calcite - Wikipedia

    en.wikipedia.org/wiki/Calcite

    Calcite. Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO 3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratch hardness comparison. Large calcite crystals are used in optical equipment, and limestone ...

  6. Calcium cycle - Wikipedia

    en.wikipedia.org/wiki/Calcium_cycle

    The calcium cycle is a transfer of calcium between dissolved and solid phases. There is a continuous supply of calcium ions into waterways from rocks, organisms, and soils. [1] [2] Calcium ions are consumed and removed from aqueous environments as they react to form insoluble structures such as calcium carbonate and calcium silicate, [1] [3] which can deposit to form sediments or the ...

  7. Hyperparathyroidism - Wikipedia

    en.wikipedia.org/wiki/Hyperparathyroidism

    Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. [1][4] This occurs from a disorder either within the parathyroid glands (primary hyperparathyroidism) or as response to external stimuli (secondary hyperparathyroidism). [1] Symptoms of hyperparathyroidism are caused by inappropriately normal or elevated blood ...

  8. Isotopes of calcium - Wikipedia

    en.wikipedia.org/wiki/Isotopes_of_calcium

    Calcium (20 Ca) has 26 known isotopes, ranging from 35 Ca to 60 Ca. There are five stable isotopes (40 Ca, 42 Ca, 43 Ca, 44 Ca and 46 Ca), plus one isotope (48 Ca) with such a long half-life that it is for all practical purposes stable. The most abundant isotope, 40 Ca, as well as the rare 46 Ca, are theoretically unstable on energetic grounds ...

  9. Mineral (nutrient) - Wikipedia

    en.wikipedia.org/wiki/Mineral_(nutrient)

    In the context of nutrition, a mineral is a chemical element. Some "minerals" are essential for life, but most are not. [1][2][3] Minerals are one of the four groups of essential nutrients; the others are vitamins, essential fatty acids, and essential amino acids. [4] The five major minerals in the human body are calcium, phosphorus, potassium ...