Definition Kidney stones are formed from a hard mineral deposit called calculus. Calculus is a “result of a chemical reaction that occurs when the urine becomes too concentrated. Calcium salts, uric acid, cystine, and other substances in the urine crystallize to form a (stone), often the size of a pebble.” (Mayo Clinic Family Health Book, p. 898) The most common types of kidney stones are: Calcium stones, account for over 70% of all stones; found mostly in men Uric acid stones, account for approximately 8% of all stones; also found mostly in men  Symptoms Kidney stones generally don’t produce symptoms until they break loose and begin to work their way.