Calcium strontium or barium, the oxide–nitride coating that results in air is stable and lathe machining and other standard metallurgical techniques are suitable for calcium. In the United States and Canada, calcium is instead produced by reducing lime with aluminium at high temperatures. Calcium provides a link between tectonics, climate, and the carbon cycle. In the simplest terms, uplift of mountains exposes calcium-bearing rocks to chemical weathering and releases Ca into surface water. These ions are transported to the ocean where they react with dissolved CO to form limestone (), which in turn settles to the sea floor where it is
Calcium in biology effective January 1, 2010. Examples of allowed wording are shown below. In order to qualify for the calcium health claim, a dietary supplement much contain at least 20% of the Reference Dietary Intake, which for calcium means at least 260 mg/serving. In 2005 the FDA approved a Qualified Health Claim for calcium and hypertension, with suggested wording "Some scientific evidence suggests that calcium supplements may reduce the risk of hypertension. However, FDA has determined that the evidence is inconsistent and not conclusive." Evidence for pregnancy-induced hypertension and preeclamsia was considered inconclusive. The same year the FDA approved a QHC for