Kidney Stones I The kidney stone is a solid, crystalline mineral that forms within the urinary tract or kidney and is often created from the chemicals found in urine. A kidney stone starts to develop when there is a lot of waste in a small amount of liquid. The stone attracts other materials or elements to create a larger stone. Typically, kidney stones leave the human body by passing out in a stream of urine. These stones can be as large as pearls, similar in size as grains of sand, or as large as golf balls. The blockage of urine flow by a stone or stones often results in extreme pain. Apart from that, a stone may disintegrate and travel along the urine tract and out of the body without necessarily causing pain or too much discomfort