This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
Calcium is a grayish-white metal, the basic radical of lime, and its compounds: as a carbonate it occurs naturally in chalk, marble, etc.; as a sulphate in gypsum; as phosphate and carbonate in shells, bones, and various organic tissues; and as silicate and fluoride in various minerals and vegetables. When heated, it becomes quickly oxidized and converted into lime - calx: inflamed, it burns with a bright light.