Calcium Calcium Calcium is a chemical element with 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 the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The
Society for Scientific Exploration X-Files or in the National Enquirer shows up first here. But what also shows up is a surprising attitude of skepticism." The society's magazine, the "Journal of Scientific Exploration", was established to provide a scientific forum for ufology, parapsychology and cryptozoology, having published research articles, essays, book reviews and letters on those and many other topics that are largely ignored in mainstream journals. The journal is currently edited by parapsychologist and philosopher Stephen E. Braude. The Spirituality and Psychiatry Special Interest Group of the Royal College of Psychiatrists says that the journal has reports about anomalies in science, particularly in