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.

有一结石是氨酸结石，是氨酸渗入尿液后结晶色或者淡粉色的结石，在X线下是不透光的。