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
Symbol Hence, "outward sign" of something. The meaning "something which stands for something else" was first recorded in 1590, in Edmund Spenser's "Faerie Queene". In considering the effect of a symbol on the psyche, in his seminal essay "The Symbol without Meaning" Joseph Campbell proposes the following definition: "A symbol is an energy evoking, and directing, agent". Later, expanding on what he means by this definition Campbell says: Jared Elisha defined symbolism that is something that stands for another, it can be place, object, or a person Heinrich Zimmer gives a concise overview of the nature, and perennial relevance, of symbols.