Courtney -. In nature, calcium is found in rocks, chalk, and seashells. It is found in the bones, muscles, and nerves of animals and in many different plants.In the food you eat, there is a lot of calcium in milk and other dairy products. There is also a good deal of calcium in green leafy vegetables like spinach.alcium is the main constituent of bones mainly in the chemical form of Calcium phosphate. So essentially calcium is found everywhere in normal bones.