<prompt> Renal calculi are commonly made up ofCalcium oxalateMagnesium ammonium phosphateUric acidCystine  <response>: There are four main types of kidney stones Calcium stones are the most common type of kidney stones. They are usually made of calcium and oxalate a natural chemical found in most foods, but are sometimesmade of calcium and phosphate. Uric acid stones form when your urine is often too acidic. Refer robbins 9e p951 