All of the following form radiolucent stones except:

Plain radiograph  Calcium-containing stones are radiopaque:  Calcium oxalate +/- calcium phosphate  Struvite (triple phosphate) - usually opaque, but variable  Pure calcium phosphate  Lucent stones include:  Uric acid  Cystine Medication (indinavir is best known) stones  Pure matrix stones (although may have a radiodense rim or centre)  Key Point: Cysteine and Cystine are different amino acids.