Calcium Hydroxyapatite by Solaray is a Micro-crystalline, dietary supplement. Calcium Hydoxyapatite is the microcrystalline form of calcium and phosphorus in the exact ratio formed by the body. Microcrystaline hydroxyapatite (MCHC), a variation on bonemeal, has attracted attention because it causes increases in bone mass and better effects on bone mass than calcium carbonate. Hydoxyapatite Calcium is one of the most absorbable and effective forms of calcium for the prevention of bone loss. The surface of hydroxyapatite helps attract and hold in reserve the Potassium, Magnesium, Boron, Zinc, Silica, and Chromium that are also included in this powerful product.