A tiny minority of stones are cystine stones, composed of the amino acid cystine which sometimes leaks into the urine to crystalize and form a yellow or light pink colored stone that is radiopaque under X-ray.

有一小部分结石是氨酸结石，是氨酸渗入液后结晶形成黄色粉色的结石，在X线下是不透光的。