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Natural calcium is a mixture of five stable isotopes (40 Ca, 42 Ca, 43 Ca, 44 Ca, and 46 Ca) and one isotope with a half-life so long that it is for all practical purposes stable (48 Ca, with a half-life of about 4.3 × 10 19 years). Calcium is the first (lightest) element to have six naturally occurring isotopes. [14]
Calcium makes up 920 to 1200 grams of adult body weight, with 99% of it contained in bones and teeth. This is about 1.5% of body weight. [ 2 ] Phosphorus occurs in amounts of about 2/3 of calcium, and makes up about 1% of a person's body weight. [ 10 ]
Calcium carbonate is also used as a firming agent in many canned and bottled vegetable products. Several calcium supplement formulations have been documented to contain the chemical element lead, [69] posing a public health concern. [70] Lead is commonly found in natural sources of calcium. [69]
Calcium-60 is the heaviest known isotope as of 2020. [1] First observed in 2018 at Riken alongside 59 Ca and seven isotopes of other elements, [26] its existence suggests that there are additional even-N isotopes of calcium up to at least 70 Ca, while 59 Ca is probably the last bound isotope with odd N. [27]
Ca and Mg are found in nature in many compounds such as dolomite, aragonite, magnesite (carbonate rocks). Calcium and magnesium ions are found in hard water. Hard water represents a multifold issue. It is of great interest to remove these ions, thus softening the water.
Many plants accumulate calcium oxalate crystals in response to surplus calcium, which is found throughout the natural environment. The crystals are produced in a variety of shapes. The crystal morphology depends on the taxonomic group of the plant.
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 U.S. Institute of Medicine (IOM) established Recommended Dietary Allowances (RDAs) for calcium in 1997 and updated those values in 2011. [6] See table. The European Food Safety Authority (EFSA) uses the term Population Reference Intake (PRIs) instead of RDAs and sets slightly different numbers: ages 4–10 800 mg, ages 11–17 1150 mg, ages 18–24 1000 mg, and >25 years 950 mg. [10]