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 carbonate 170. Used as an acidity regulator, anticaking agent, stabiliser or colour it is approved for usage in the EU, USA and Australia and New Zealand. It is used in some soy milk and almond milk products as a source of dietary calcium; one study suggests that calcium carbonate might be as bioavailable as the calcium in cow's milk. Calcium carbonate is also used as a firming agent in many canned or bottled vegetable products. Agricultural lime, powdered chalk or limestone, is used as a cheap method for neutralising acidic soil, making it suitable for planting. Calcium carbonate is a key