Kidney stones are clumps developed from solidified crystals in the kidney or urinary tract. The urine has all the ingredients that form the stone, but all these ideally pass through without our knowledge. When there is an imbalance in any of these substances, the crystals cluster together into stones. The size of the stone can be as small as a grain of sand to one as large as the size of a golf ball. The most commonly found kidney stone in humans is usually made of calcium oxalate. Other rare varieties of kidney stones include those made up of cystine, struvite (magnesium, ammonium, and phosphate), calcium phosphate, uric acid, etc.